| 1. |
- Alstermark, Bror, et al.
(författare)
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Anders Lundberg (1920-2009)
- 2010
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Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 200:3-4, s. 193-195
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Anders Lundberg was one of the founding editorial board members for EBR when it began its life in 1976 under the editorship of John Eccles. He was also one of the most prolific contributors to the journal with a total of 49 papers, including a series of 16 on the topic of "integration in descending motor pathways controlling the forelimb in the cat". He continued as an editor of the journal until volume 16 when he persuaded his younger colleague Hans Hultborn to take his place. Hans is one of the authors of the obituary. –John Rothwell
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| 2. |
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| 3. |
- Angel, Michael J., et al.
(författare)
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Candidate interneurones mediating group I disynaptic EPSPs in extensor motoneurones during fictive locomotion in the cat.
- 2005
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 563:Pt 2, s. 597-610
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we sought to find interneurones responsible for the group I-evoked disynaptic excitation of hindlimb extensor motoneurones that occurs during fictive locomotion. Locomotion was produced by stimulation of the mesencephalic locomotor region (MLR) in decerebrate paralysed cats in which activation of ankle extensor group I afferents evoked a disynaptic excitation of motoneurones during the extension phase of fictive locomotion. Extracellular recordings were used to locate interneurones fulfilling all, or five of the six following criteria: (i) weak or no response to stimulation of extensor group I afferents in the absence of locomotion; (ii) strong group I activation during locomotion; (iii) group I activation at monosynaptic latencies; (iv) strong group I activation during only the extensor phase of locomotion; and (v) antidromic activation from the extensor motor nuclei; but (vi) no antidromic activation from rostral spinal segments. Candidate excitatory interneurones were located in mid to caudal parts of the L7 segments in areas where monosynaptic field potentials were evoked by group I afferents, within 2 mm of the stimulation site in the ventral horn from which they were antidromically activated. All were activated during extension by stimulation of group I afferents in extensor nerves. In the absence of peripheral nerve stimulation, six of the seven candidate excitatory interneurones were rhythmically active with maximal activation during the extension phase of fictive locomotion. Rhythmic activity during extension was also seen in five additional interneurones located near candidate interneurones but not activated by group I strength stimulation of the tested nerves. We suggest that the lumbosacral interneurones located in the intermediate laminae that can be activated by extensor group I afferents during the extension phase are a previously unknown population of interneurones, and may mediate group I-evoked disynaptic excitation of extensor motoneurones. Their rhythmic activity suggests that they also provide central excitatory drive to extensor motoneurones during locomotion.
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| 4. |
- Asanuma, H., et al.
(författare)
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Projection of individual pyramidal tract neurons to lumbar motor nuclei of the monkey
- 1979
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 34, s. 73-89
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Tidskriftsartikel (refereegranskat)abstract
- The projection of individual pyramidal tract (PT) neurons from the hindlimb area in the precentral gyrus of the cerebral cortex to the lumbar spinal cord was studied in the monkey by systematically searching for sites within identified regions of the spinal gray from which the PT neurons could be antidromically activated by local stimulation. All investigated neurons belonged to the fast conducting fraction of PT neurons. The following results were obtained. 1. Each PT neuron could be activated from more than one region of the spinal gray matter, including identified spinal motor nuclei and areas dorsomedial to these nuclei, but not the intermediate nucleus or regions dorsal to it. "Passage areas" and "termination areas" were defined. 2. Half of the PT neurons with termination areas within motor nuclei had these areas in more than one nucleus. There were thus strong suggestions for synaptic contacts of some PT neurons with motoneurons of more than one muscle. 3. Four groups of three or four neurons were recorded simultaneously by the same cortical electrode. Comparisons of passage and termination areas within groups revealed both similarities and differences in projections of neighboring neurons. Every neuron was activated from some region(s) where others of the group were not. Common passage areas, or passage and termination areas, for two or three neurons of a group within at least one motor nucleus were found for all groups. Termination areas in the same motor nucleus have been found for the majority of the neurons of only one group. These common projection areas are compatible with, but do not prove, that a group of adjacent PT neurons has common target cells in the spinal cord. © 1979 Springer-Verlag.
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| 5. |
- Baczyk, Marcin, et al.
(författare)
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Facilitation of ipsilateral actions of corticospinal tract neurons on feline motoneurons by transcranial direct current stimulation
- 2014
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X. ; 40:4, s. 2628-2640
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Tidskriftsartikel (refereegranskat)abstract
- Ipsilateral actions of pyramidal tract (PT) neurons are weak but may, if strengthened, compensate for deficient crossed PT actions following brain damage. The purpose of the present study was to examine whether transcranial direct current stimulation (tDCS) can strengthen ipsilateral PT (iPT) actions; in particular, those relayed by reticulospinal neurons co-excited by axon collaterals of fibres descending in the iPT and contralateral PT (coPT) and of reticulospinal neurons descending in the medial longitudinal fascicle (MLF). The effects of tDCS were assessed in acute experiments on deeply anaesthetized cats by comparing postsynaptic potentials evoked in hindlimb motoneurons and discharges recorded from their axons in a ventral root, before, during and after tDCS. tDCS was consistently found to facilitate joint actions of the iPT and coPT, especially when they were stimulated together with the MLF. Both excitatory postsynaptic potentials and inhibitory postsynaptic potentials evoked in motoneurons and the ensuing ventral root discharges were facilitated, even though the facilitatory effects of tDCS were not sufficient for activation of motoneurons by iPT neurons alone. Facilitation outlasted single tDCS periods by at least a few minutes, and the effects evoked by repeated tDCS by up to 2 h. The results of this study thus indicate that tDCS may increase the contribution of iPT actions to the recovery of motor functions after injuries to coPT neurons, and thereby assist rehabilitation, provided that corticoreticular and reticulospinal connections are preserved.
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| 6. |
- Baczyk, Marcin, et al.
(författare)
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Long-term effects of direct current are reproduced by intermittent depolarization of myelinated nerve fibers
- 2018
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 120:3, s. 1173-1185
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Tidskriftsartikel (refereegranskat)abstract
- Direct current (DC) potently increases the excitability of myelinated afferent fibers in the dorsal columns, both during DC polarization of these fibers and during a considerable (>1 h) postpolarization period. The aim of the present study was to investigate whether similarly long-lasting changes in the excitability of myelinated nerve fibers in the dorsal columns may be evoked by field potentials following stimulation of peripheral afferents and by subthreshold epidurally applied current pulses. The experiments were performed in deeply anesthetized rats. The effects were monitored by changes in nerve volleys evoked in epidurally stimulated hindlimb afferents and in the synaptic actions of these afferents. Both were found to be facilitated during as well as following stimulation of a skin nerve and during as well as following epidurally applied current pulses of 5- to 10-ms duration. The facilitation occurring <= 2 min after skin nerve stimulation could be linked to both primary afferent depolarization and large dorsal horn field potentials, whereas the subsequent changes (up to 1 h) were attributable to effects of the field potentials. The findings lead to the conclusion that the modulation of spinal activity evoked by DC does not require long-lasting polarization and that relatively short current pulses and intrinsic field potentials may contribute to plasticity in spinal activity. These results suggest the possibility of enhancing the effects of epidural stimulation in human subjects by combining it with polarizing current pulses and peripheral afferent stimulation and not only with continuous DC. NEW & NOTEWORTHY The aim of this study was to define conditions under which a long-term. increase is evoked in the excitability of myelinated nerve fibers. The results demonstrate that a potent and long-lasting increase in the excitability of afferent fibers traversing the dorsal columns may be induced by synaptically evoked intrinsic field as well as by epidurally applied intermittent current pulses. They thus provide a new means for the facilitation of the effects of epidural stimulation.
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| 7. |
- Baczyk, Marcin, et al.
(författare)
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Presynaptic actions of transcranial and local direct current stimulation in the red nucleus
- 2014
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 592:Pt 19, s. 4313-28
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Tidskriftsartikel (refereegranskat)abstract
- The main aim of the present study was to examine to what extent long-lasting subcortical actions of transcranial direct current stimulation (tDCS) may be related to its presynaptic actions. This was investigated in the red nucleus, where tDCS was recently demonstrated to facilitate transmission between interpositorubral and rubrospinal neurons. Changes in the excitability of preterminal axonal branches of interpositorubral neurons close to rubrospinal neurons were investigated during and after tDCS (0.2 mA) applied over the sensorimotor cortical area in deeply anaesthetized rats and cats. As a measure of the excitability, we used the probability of antidromic activation of individual interpositorubral neurons by electrical stimuli applied in the red nucleus. Our second aim was to compare effects of weak (≤1 μA) direct current applied within the red nucleus with effects of tDCS to allow the use of local depolarization in a further analysis of mechanisms of tDCS instead of widespread and more difficult to control depolarization evoked by distant electrodes. Local cathodal polarization was found to replicate all effects of cathodal tDCS hitherto demonstrated in the rat, including long-lasting facilitation of trans-synaptically evoked descending volleys and trisynaptically evoked EMG responses in neck muscles. It also replicated all effects of anodal tDCS in the cat. In both species, it increased the excitability of preterminal axonal branches of interpositorubral neurons up to 1 h post-tDCS. Local anodal polarization evoked opposite effects. We thus show that presynaptic actions of polarizing direct current may contribute to both immediate and prolonged effects of tDCS. © 2014 The Physiological Society.
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| 8. |
- Bannatyne, B Anne, et al.
(författare)
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Differential projections of excitatory and inhibitory dorsal horn interneurons relaying information from group II muscle afferents in the cat spinal cord.
- 2006
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 26:11, s. 2871-80
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Tidskriftsartikel (refereegranskat)abstract
- Dorsal horn interneurons with input from group II muscle spindle afferents are components of networks involved in motor control. Thirteen dorsal horn interneurons with monosynaptic group II input were characterized electrophysiologically and labeled intracellularly with Neurobiotin. Their axonal projections were traced, and neurotransmitter content was established by using immunocytochemistry. Two subpopulations were identified: five interneurons had axons that contained vesicular glutamate transporter 2 and hence were glutamatergic and excitatory. Terminals of the remaining eight interneurons were immunoreactive for the glycine transporter 2 or were apposed to gephyrin but did not contain the GABA-synthesizing enzyme glutamic acid decarboxylase and were therefore glycinergic and inhibitory. Excitatory cells were located mainly in the central region of lamina IV and had relatively small somata and restricted dendritic trees. In contrast, inhibitory interneurons were located more ventrally, in lamina V and had relatively larger somata and more extensive dendritic trees. Axonal projections of the two subpopulations differed considerably. Excitatory interneurons predominantly projected ipsilaterally, whereas most inhibitory interneurons projected both ipsilaterally and contralaterally. Three inhibitory axons formed contacts with large cholinergic cells in motor nuclei, thus revealing a novel direct coupling between inhibitory dorsal horn interneurons and motoneurons. The organization of the excitatory interneurons is consistent with current knowledge of reflex pathways to motoneurons, but the existence and connections of the inhibitory subpopulation could not be predicted from previous data. Our results indicate that these latter interneurons exercise widespread inhibitory control over a variety of cell types located on both sides of the spinal cord.
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| 9. |
- Bannatyne, B A, et al.
(författare)
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Excitatory and inhibitory intermediate zone interneurons in pathways from feline group I and II afferents: differences in axonal projections and input.
- 2009
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Ingår i: The Journal of physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 587:Pt 2, s. 379-99
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to compare properties of excitatory and inhibitory spinal intermediate zone interneurons in pathways from group I and II muscle afferents in the cat. Interneurons were labelled intracellularly and their transmitter phenotypes were defined by using immunocytochemistry. In total 14 glutamatergic, 22 glycinergic and 2 GABAergic/glycinergic interneurons were retrieved. All interneurons were located in laminae V-VII of the L3-L7 segments. No consistent differences were found in the location, the soma sizes or the extent of the dendritic trees of excitatory and inhibitory interneurons. However, major differences were found in their axonal projections; excitatory interneurons projected either ipsilaterally, bilaterally or contralaterally, while inhibitory interneurons projected exclusively ipsilaterally. Terminal projections of glycinergic and glutamatergic cells were found within motor nuclei as well as other regions of the grey matter which include the intermediate region, laminae VII and VIII. Cells containing GABA/glycine had more restricted projections, principally within the intermediate zone where they formed appositions with glutamatergic axon terminals and unidentified cells and therefore are likely to be involved in presynaptic as well as postsynaptic inhibition. The majority of excitatory and inhibitory interneurons were found to be coexcited by group I and II afferents (monosynaptically) and by reticulospinal neurons (mono- or disynaptically) and to integrate information from several muscles. Taken together the morphological and electrophysiological data show that individual excitatory and inhibitory intermediate zone interneurons may operate in a highly differentiated way and thereby contribute to a variety of motor synergies.
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| 10. |
- Bannatyne, B A, et al.
(författare)
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Inhibitory inputs to four types of spinocerebellar tract neurons in the cat spinal cord.
- 2012
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Ingår i: Neuroscience. - : Elsevier BV. - 1873-7544 .- 0306-4522. ; 226, s. 253-69
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Tidskriftsartikel (refereegranskat)abstract
- Spinocerebellar tract neurons are inhibited by various sources of input via pathways activated by descending tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with ventral spinocerebellar tract (VSCT) and dorsal spinocerebellar tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of spinocerebellar tract neurons to the cerebellum.
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| 11. |
- Bannatyne, B Anne, et al.
(författare)
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Networks of inhibitory and excitatory commissural interneurons mediating crossed reticulospinal actions.
- 2003
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Ingår i: The European journal of neuroscience. - 0953-816X. ; 18:8, s. 2273-84
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Tidskriftsartikel (refereegranskat)abstract
- Axonal projections and neurotransmitters used by commissural interneurons mediating crossed actions of reticulospinal neurons were investigated in adult cats. Eighteen interneurons, located in or close to lamina VIII in midlumbar segments, that were monosynaptically excited by reticulospinal tract fibres and projected to contralateral motor nuclei were labelled by intracellular injection of tetramethylrhodamine-dextran and Neurobiotin. The nine most completely labelled interneurons were analysed with combined confocal and light microscopy. None of the stem axons gave off ipsilateral axon collaterals. Seven cells had axon collaterals that arborized in the contralateral grey matter in the ventral horn of the same segments. Transmitters were identified by using antibodies raised against vesicular glutamate transporters 1 and 2, glutamic acid decarboxylase and the glycine transporter 2. The axons of two cells were immunoreactive for the glycine transporter 2 and hence were glycinergic. Three cells were immunoreactive for the vesicular glutamate transporter 2 and hence were glutamatergic. None of the axons displayed immunoreactivity for glutamic acid decarboxylase. Electron microscopy of two cells revealed direct synaptic connections with motoneurons and other neurons. Axonal swellings of one neuron formed synapses with profiles in motor nuclei whereas those of the other formed synapses with other structures, including cell bodies in lamina VII. The results show that this population of commissural interneurons includes both excitatory and inhibitory cells that may excite or inhibit contralateral motoneurons directly. They may also influence the activity of motoneurons indirectly by acting through interneurons located outside motor nuclei in the contralateral grey matter but are unlikely to have direct actions on interneurons in the ipsilateral grey matter.
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| 12. |
- Barker, D., et al.
(författare)
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Identification of intrafusal muscle fibres activated by single fusimotor axons and injected with fluorescent dye in cat tenuissimus spindles.
- 1978
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 275, s. 149-165
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Tidskriftsartikel (refereegranskat)abstract
- 1. Intrafusal muscle fibres of cat tenuissimus spindles have been injected with the fluorescent dye Procion Yellow and identified histologically after recording their changes in membrane potential during 1/sec stimulation of single static or dynamic gamma axons. 2. Thirteen intrafusal muscle fibres innervated by static gamma axons were identified as eight bag2 and five chain fibres. The fact that none proved to be a bag1 fibre is not regarded as significant, for reasons given in the Discussion. 3. In one spindle Procion Yellow was injected into two intrafusal muscle fibres activated by the same static gamma axon; they were identified as a bag2 and a chain fibre. 4. Nine intrafusal muscle fibres innervated by dynamic gamma axons were identified as seven bag1 fibres, one bag2 fibre, and one long chain fibre. 5. In one spindle two bag fibres were injected, one activated by a dynamic gamma axon, the other by a static gamma axon; the former proved to be a bag1 fibre, the latter a bag2 fibre. 6. Stimulation of static gamma axons elicited junctional potentials in seven bag2 fibres and one damaged chain fibre, and action potentials in one bag2 and four chain fibres. In the whole sample of impaled intrafusal muscle fibres (identified and unidentified) activated by static axons, junctional potentials were recorded from twenty‐three (62.2%), and action potentials from fourteen (37.8%). Stimulation of dynamic gamma axons always elicited junctional potentials. 7. In a number of instances it was possible to examine the ultrastructure of motor endings belonging to the stimulated gamma axon. The myoneural junctions of trail endings supplied by static gamma axons to bag2 and chain fibres were both smooth and folded; the deepest and most regular folding occurred on chain fibres. The terminals of p2 plates supplied to bag1 fibres by dynamic gamma axons had smooth myoneural junctions. © 1978 The Physiological Society
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| 13. |
- Bolzoni, Francesco, et al.
(författare)
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Direct current stimulation modulates the excitability of the sensory and motor fibres in the human posterior tibial nerve, with a long-lasting effect on the H-reflex
- 2017
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X. ; 46:9, s. 2499-2506
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Tidskriftsartikel (refereegranskat)abstract
- Several studies demonstrated that transcutaneous direct current stimulation (DCS) may modulate central nervous system excitability. However, much less is known about how DC affects peripheral nerve fibres. We investigated the action of DCS on motor and sensory fibres of the human posterior tibial nerve, with supplementary analysis in acute experiments on rats. In forty human subjects, electric pulses at the popliteal fossa were used to elicit either M-waves or H-reflexes in the Soleus, before (15 min), during (10 min) and after (30 min) DCS. Cathodal or anodal current (2 mA) was applied to the same nerve. Cathodal DCS significantly increased the H-reflex amplitude; the post-polarization effect lasted up to similar to 25 min after the termination of DCS. Anodal DCS instead significantly decreased the reflex amplitude for up to similar to 5 min after DCS end. DCS effects on M-wave showed the same polarity dependence but with considerably shorter after-effects, which never exceeded 5 min. DCS changed the excitability of both motor and sensory fibres. These effects and especially the long-lasting modulation of the H-reflex suggest a possible rehabilitative application of DCS that could be applied either to compensate an altered peripheral excitability or to modulate the afferent transmission to spinal and supraspinal structures. In animal experiments, DCS was applied, under anaesthesia, to either the exposed peroneus nerve or its Dorsal Root, and its effects closely resembled those found in human subjects. They validate therefore the use of the animal models for future investigations on the DCS mechanisms.
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| 14. |
- Bolzoni, Francesco, et al.
(författare)
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Ephaptic interactions between myelinated nerve fibres of rodent peripheral nerves
- 2019
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 50:7, s. 3101-3107
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Tidskriftsartikel (refereegranskat)abstract
- We report evidence that ephaptic interactions may occur between intact mammalian myelinated nerve fibres and not only between demyelinated or damaged mammalian nerve fibres or nerve cells as analysed in previous studies. The ephaptic interactions were investigated between nerve fibres traversing the lumbar dorsal roots and between bundles of fibres in the sciatic nerve in anaesthetized rats in vivo. The interactions were estimated by comparing the excitability of nerve fibres originating from one of the hindlimb nerves (peroneal or sural) under control conditions and when the stimulation of these fibres was combined with stimulation of another nerve (tibial). An increase in nerve volleys recorded from group I muscle afferents in the peroneal nerve and of the fastest skin afferents in the sural nerve was used as a measure of the increase in the excitability. The excitability of these fibres was increased during a fraction of a millisecond, coinciding with the period of passage of nerve impulses evoked by the conditioning stimulation of the tibial nerve. The degree of the increase was comparable to the increases in the excitability evoked by 1–2min lasting fibre polarization. Ephaptic interactions were found to be more potent and with longer lasting after-effects within the dorsal roots than within the sciatic nerve. We postulate that ephaptic interactions may result in the synchronization of information forwarded via neighbouring afferent nerve fibres prior to their entry into the spinal cord and thereby securing the propagation of nerve impulses across branching points within the spinal grey matter. © 2019 Federation of European Neuroscience Societies and John Wiley & Sons Ltd
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| 15. |
- Bolzoni, Francesco, et al.
(författare)
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Evidence for long-lasting subcortical facilitation by transcranial direct current stimulation in the cat
- 2013
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Ingår i: The Journal of physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 591, s. 3381-3399
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Tidskriftsartikel (refereegranskat)abstract
- The main aim of the study was to examine effects of transcranial polarization on neurons in two descending motor systems, rubro- and reticulo-spinal. Anodal DC current was applied through an electrode in contact with the skull over the contralateral sensori-motor cortex, against an electrode placed between the skull and the ipsilateral temporal muscles in deeply anaesthetized cats. Its effects were estimated from changes in descending volleys evoked by electrical stimuli applied in the Red Nucleus (RN), Medial Longitudinal Fascicle (MLF; to reticulospinal fibres) and the Pyramidal Tract (PT; to corticospinal or corticoreticular fibres). The descending volleys were recorded from the surface of the spinal cord at a cervical level. Rubrospinal neurones were activated either directly or indirectly, via interpositorubral fibres. Reticulospinal neurons were likewise activated directly and indirectly, via other reticulospinal or corticospinal fibres. Transcranial polarization facilitated transsynaptic activation of both rubrospinal and reticulospinal neurons, shortening the latency of the indirect descending volleys and/or increasing them, Direct activation of descending axons was much less affected. The facilitation of all subcortical neurons examined was potentiated by repeated applications of tDCS and outlasted the polarization by at least 1-2 hours, replicating tDCS effects on indirect activation of cortical neurons. The results indicate that beneficial effects of tDCS on motor performance in humans may be due to more efficient activation not only of cortical but also subcortical neuronal systems. Combined actions of tDCS on cortical and subcortical neurones might thus further improve recovery of motor functions during rehabilitation after central injuries.
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| 16. |
- Bolzoni, Francesco, et al.
(författare)
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Interactions Between Baclofen and DC-induced Plasticity of Afferent Fibers within the Spinal Cord
- 2019
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Ingår i: Neuroscience. - : Elsevier BV. - 0306-4522. ; 404, s. 119-129
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the study were to compare effects of baclofen, a GABA(B) receptor agonist commonly used as an antispastic drug, on direct current (DC) evoked long-lasting changes in the excitability of afferent fibers traversing the dorsal columns and their terminal branches in the spinal cord, and to examine whether baclofen interferes with the development and expression of these changes. The experiments were performed on deeply anesthetized rats by analyzing the effects of DC before, during and following baclofen administration. Muscle and skin afferent fibers within the dorsal columns were stimulated epidurally and changes in their excitability were investigated following epidural polarization by 1.0-1.1 mu A subsequent to i.v. administration of baclofen. Epidural polarization increased the excitability of these fibers during post-polarization periods of at least 1 h. The facilitation was as potent as in preparations that were not pretreated with baclofen, indicating that the advantages of combining epidural polarization with epidural stimulation would not be endangered by pharmacological antispastic treatment with baclofen. In contrast, baclofen-reduced effects of intraspinal stimulation combined with intraspinal polarization (0.3 mu A) of terminal axonal branches of the afferents within the dorsal horn or in motor nuclei, whether administered ionophoretically or intravenously. Effects of DC on monosynaptically evoked synaptic actions of these fibers (extracellular field potentials) were likewise reduced by baclofen. The study thus provides further evidence for differential effects of DC on afferent fibers in the dorsal columns and the preterminal branches of these fibers and their involvement in spinal plasticity. (C) 2019 IBRO. Published by Elsevier Ltd. All rights reserved.
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| 17. |
- Bolzoni, Francesco, et al.
(författare)
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Presynaptic and postsynaptic effects of local cathodal DC polarization within the spinal cord in anaesthetized animal preparations
- 2015
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751. ; 593:4, s. 947-966
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Tidskriftsartikel (refereegranskat)abstract
- Key points: Trans-spinal DC stimulation affects both postsynaptic neurons and the presynaptic axons providing input to these neurons. In the present study, we show that intraspinally applied cathodal current replicates the effects of trans-spinal direct current stimulation in deeply anaesthetized animals and affects spinal neurons both during the actual current application and during a post-polarization period. Presynaptic effects of local cathodal polarization were expressed in an increase in the excitability of skin afferents (in the dorsal horn) and group Ia afferents (in motor nuclei), both during and at least 30 min after DC application. However, although the postsynaptic facilitation (i.e. more effective) activation of motoneurons by stimuli applied in a motor nucleus was very potent during local DC application, it was only negligible once DC was discontinued. The results suggest that the prolonged effects of cathodal polarization are primarily associated with changes in synaptic transmission. The present study aimed to compare presynaptic and postsynaptic actions of direct current polarization in the spinal cord, focusing on DC effects on primary afferents and motoneurons. To reduce the directly affected spinal cord region, a weak polarizing direct current (0.1-0.3 μA) was applied locally in deeply anaesthetized cats and rats; within the hindlimb motor nuclei in the caudal lumbar segments, or in the dorsal horn within the terminal projection area of low threshold skin afferents. Changes in the excitability of primary afferents activated by intraspinal stimuli (20-50 μA) were estimated using increases or decreases in compound action potentials recorded from the dorsal roots or peripheral nerves as their measure. Changes in the postsynaptic actions of the afferents were assessed from intracellularly recorded monosynaptic EPSPs in hindlimb motoneurons and monosynaptic extracellular field potentials (evoked by group Ia afferents in motor nuclei, or by low threshold cutaneous afferents in the dorsal horn). The excitability of motoneurons activated by intraspinal stimuli was assessed using intracellular records or motoneuronal discharges recorded from a ventral root or a muscle nerve. Cathodal polarization was found to affect motoneurons and afferents providing input to them to a different extent. The excitability of both was markedly increased during DC application, although post-polarization facilitation was found to involve presynaptic afferents and some of their postsynaptic actions, but only negligibly motoneurons themselves. Taken together, these results indicate that long-lasting post-polarization facilitation of spinal activity induced by locally applied cathodal current primarily reflects the facilitation of synaptic transmission.
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| 18. |
- Bolzoni, Francesco, et al.
(författare)
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Subcortical effects of transcranial direct current stimulation (tDCS) in the rat.
- 2013
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Ingår i: The Journal of physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 591:16, s. 4027-4042
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Tidskriftsartikel (refereegranskat)abstract
- Transcranial direct current stimulation (tDCS) affects neurons at both cortical and subcortical levels. The subcortical effects involve several descending motor systems but appeared to be relatively weak, as only small increases in the amplitude of subcortically initiated descending volleys and a minute shortening of latencies of these volleys were found. The aim of the present study was therefore to evaluate the consequences of facilitation of these volleys on the ensuing muscle activation. The experiments were carried on deeply anaesthetized but not paralyzed rats. Effects of tDCS were tested on EMG potentials recorded from neck muscles evoked by weak (20-60 µA) single, double or triple stimuli applied in the medial longitudinal fascicle (MLF) or in the red nucleus (RN). Short latencies of these potentials were compatible with monosynaptic or disynaptic actions of reticulo-spinal and disynaptic or trisynaptic actions of rubro-spinal neurons on neck motoneurons. Despite only weak effects on indirect descending volleys, the EMG responses from both the MLF and the RN were potently facilitated by cathodal tDCS and depressed by anodal tDCS. Both the facilitation and the depression developed relatively rapidly (within the first minute) but both outlasted tDCS and were present for up to 1 hour after tDCS. The study thus demonstrates long-lasting effects of tDCS on subcortical neurons in the rat, albeit evoked by opposite polarity of tDCS than on subcortical neurons in the cat investigated in the preceding study, or on cortical neurons in the humans.
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| 19. |
- Bras, H., et al.
(författare)
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An investigation of local actions of ionophoretically applied DOPA in the spinal cord
- 1988
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 71, s. 447-449
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Tidskriftsartikel (refereegranskat)abstract
- Methyl-L-DOPA (L-beta-3,4-dihydroxyphenylalanine methyl ester, hydrochloride) was applied ionophoretically to investigate its effects on neurones at various locations in the cat spinal cord. Its actions were tested on monosynaptic field potentials evoked from group I and group II muscle afferents in midlumbar segments. Methyl-L-DOPA has been found to depress field potentials evoked from group II afferents in the ventral horn and in the intermediate zone but not in the dorsal horn, nor field potentials evoked from group I afferents. Its effects were the same as those of systemically applied L-DOPA (L-beta-3,4-dihydroxyphenylalanine), although weaker. © 1998 Springer-Verlag.
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| 20. |
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| 21. |
- Bras, H., et al.
(författare)
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Demonstration of initial axon collaterals of cells of origin of the ventral spinocerebellar tract in the cat
- 1988
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967 .- 1096-9861. ; 273, s. 584-592
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Tidskriftsartikel (refereegranskat)abstract
- Neurones of origin of the ventral spinocerebellar tract were stained with intracellularly applied horseradish peroxidase to investigate whether they give off any initial axon collaterals. The neurones were located in the fourth and fifth lumbar segments and were identified by their antidromic activation following stimulation in the contralateral superior cerebellar peduncle. Nine of the 23 neurones with well‐stained axons were found to give off axon collaterals soon after the axons crossed the midline. The collaterals entered the contralateral ventral horn and branched within lamina VII and the dorsal part of lamina VIII. Collaterals were found arising only from neurones located in the middle of lamina VII and from axons which took a mediorostral direction. In all of these neurones excitatory postsynaptic potentials were evoked from group Ia afferents of at least some nerves, in addition to such potentials from Ib or unidentified group I afferents, and inhibitory postsynaptic potentials were evoked from group I and II afferents. The area of terminal branching of the collaterals suggests that they may supply contralateral ventral spinocerebellar neurones with information from muscles and/or mediate crossed reflexes from group I afferents. Copyright © 1988 Alan R. Liss, Inc.
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| 22. |
- Bras, H., et al.
(författare)
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Morphology of midlumbar interneurones relaying information from group II muscle afferents in the cat spinal cord
- 1989
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Ingår i: Journal of Comparative Neurology. - : Wiley. - 0021-9967 .- 1096-9861. ; 290, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of midlumbar interneurones with peripheral input from group II muscle afferents was analysed after intracellular injection of horseradish peroxidase (HRP). Twenty‐three interneurones were stained intrasomatically and five others intra‐axonally. The majority (10 of 13) of interneurones located in lamina VII (intermediate zone and ventral horn interneurones) were found to project ipsilaterally. They had medium‐sized somata and dendrites projecting radially over a distance of more than 1 mm. All of these neurones had axons that projected caudally within the ventral part of the lateral funiculus or in the lateral part of the ventral funiculus, although four had in addition an ascending secondary axonal branch. Numerous axon collaterals were given off from these axons, both before and after they left the grey matter. The collaterals arborized within laminae VII, VIII, and IX, where they covered the area of several motor nuclei. Intra‐axonal labelling of five neurones with similar input and axon trajectories revealed several axon collaterals given off between the cell body and the terminal projection areas in L7 or S1 segments. Only three of the labelled interneurones located in lamina VII and displaying the same kind of input had axons with different destinations; their axons crossed to the opposite side of the spinal cord and ascended within the contralateral ventral funiculus. These were large neurones with extensive dendritic trees, which had fairly thick axons with initial axon collaterals that branched primarily ipsilaterally (within laminae V‐VIII). Interneurones located in lamina V and in the bordering parts of laminae IV and VI (dorsal horn interneurones; n = 10) constituted a very nonhomogenous population. They projected either ipsilaterally or contralaterally and had either ascending or descending axons running in either the lateral or ventral funiculi. Generally, dorsal horn interneurones had cell bodies smaller than those of intermediate zone and ventral horn interneurones, and their dendrites extended less extensively and less uniformly around the soma. Their initial axon collaterals branched primarily in the dorsal horn, or in lamina VII, but not in or close to the motor nuclei. Our results support the conclusions of previous physiological studies that the intermediate zone and ventral horn midlumbar interneurones with group II input and that project to motor nuclei have collateral actions on other interneurones in the L4‐L6 segments, and that dorsal horn interneurones do not project to motoneurones, but have as their targets other interneurones or ascending cells. On the other hand, we have not found any projections of L4 interneurones with input from either group I or group I1 muscle afferents, to Clarke's column, in contrast to the projections of interneurones in reflex pathways from tendon organs from more caudal segments. Copyright © 1989 Alan R. Liss, Inc.
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| 23. |
- Brink, E., et al.
(författare)
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Convergence onto interneurons subserving primary afferent depolarization of group I afferents
- 1984
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 51, s. 432-449
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to investigate whether common or independent neuronal pathways are used to evoke primary afferent depolarization (PAD) from selectively activated group Ia and Ib afferents of different muscles. To this end, the spatial facilitation of effects of various afferents, indicating convergence on the same interneurons, was used as a test. Its occurrence was assessed on dorsal root potentials (DRPs) evoked in unspecified fibers or using intra-axonal recording from identified group Ia muscle spindle afferents or group Ib tendon organ afferents. Spatial facilitation has been found in PAD pathways a) from various Ia-afferents, whether of flexors or extensors; b) from various Ib-afferents, whether of flexors or extensors; and c) from flexor Ib-afferents and flexor or extensor Ia-afferents. In contrast, no indications have been found for common pathways from extensor Ib- and any Ia-afferents under conditions that proved effective in other combinations. Latencies of those components of PAD that appeared as a result of the spatial facilitation ranged from 2 to more than 7 ms, indicating than the convergence occurred in the shortest (trisynaptic) as well as longer pathways. The same patterns of convergence have been found in PAD pathways to extensor and flexor Ia-afferents (in experiments with intraaxonal recording from these afferents). The possibility might thus be considered that some neuronal pathways are used to modulate transmission via Ia-afferents independently of their muscle origin. The same might hold true for extensor and flexor Ib-afferents. Generally, it is concluded that the minimal number of distinct neuronal populations subserving PAD of group I afferents may be two to six. Additionally, actions of cutaneous, joint, and interosseous afferents on DRPs from Ia-afferents were reexamined to further the comparison between neurons mediating PAD and those mediating postsynaptic excitation or inhibition of motoneurons. Only depression of Ia DRPs followed stimulation of these afferents at intensities of 1.5-2.0 times threshold and higher; lower threshold afferents were apparently ineffective. On the basis of lack of convergence of extensor Ib and Ia muscle afferents and of low-threshold cutaneous afferents, interneurons mediating PAD may thus be distinguished from the interneurons subserving Ib and Ia-like-Ib postsynaptic actions in motoneurons. The latter are coexcited by these three groups of afferents.
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| 24. |
- Brink, E., et al.
(författare)
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Post‐synaptic potentials in a population of motoneurones following activity of single interneurones in the cat.
- 1983
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 343, s. 341-359
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Tidskriftsartikel (refereegranskat)abstract
- The technique of recording post‐synaptic potentials from a population of motoneurones, by recording from ventral roots perfused with isotonic sucrose, has been applied to investigate the action of single last‐order interneurones; the target motoneurones were in either caudal L7 or S1 segments. Using spike‐triggered averaging, the inhibitory action of 70% of previously identified last‐order interneurones (Renshaw cells and lamina VII Ia inhibitory interneurones) has been detected. Previous observations had suggested that interneurones mediating disynaptic non‐reciprocal inhibition from group I muscle afferents should be characterized by (i) location in laminae V‐VI, (ii) monosynaptic group I input and (iii) ascending collateral axonal projection to upper lumbar segments. 65% of interneurones with these characteristics were found to inhibit motoneurones. In addition, spike‐triggered averaging from this group of laminae V‐VI interneurones sometimes revealed a depolarizing potential which preceded the inhibitory potential evoked by the interneurone. The depolarizing potential is interpreted as being due to the action of some presynaptic fibres which branch to innervate both the investigated interneurones and motoneurones. © 1983 The Physiological Society
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| 25. |
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| 26. |
- Burke, R. E., et al.
(författare)
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A comparison of peripheral and rubrospinal synaptic input to slow and fast twitch motor units of triceps surae
- 1970
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 207, s. 709-732
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Tidskriftsartikel (refereegranskat)abstract
- 1. Post‐synaptic potentials (PSPs) evoked by electrical stimulation of a variety of input systems have been compared in triceps surae motoneurones innervating slow and fast muscle units, the speed of contraction of which was also determined. 2. Stimulation of high threshold afferents in both flexor and extensor muscle nerves, and of joint afferents, evoked polysynaptic PSPs which were predominantly hyperpolarizing in both fast and slow twitch motor units. 3. Volleys in cutaneous afferents in the sural and saphenous nerves evoked polysynaptic PSPs composed of mixtures of inhibitory and excitatory components. The inhibitory components were predominant in slow twitch motor units, while in fast twitch units there was a trend towards excitatory predominance. 4. Repetitive stimulation of the red nucleus caused predominantly inhibitory PSPs in slow twitch units and mixed or predominantly excitatory PSPs in fast twitch units. There was a correlation in the excitatory/inhibitory balance between PSPs of cutaneous and rubrospinal origin in those motoneurones in which both types of PSPs were studied. 5. The amplitudes of group Ia disynaptic inhibitory PSPs were found to be correlated with motor unit twitch type: IPSPs in slow twitch units were larger than those in fast twitch units. Rubrospinal conditioning volleys were found to facilitate group Ia IPSPs in both fast and slow twitch motor units. 6. The results suggest that there may be several basic patterns of synaptic input organization to motoneurones within a given motor unit pool. In addition to quantitative variation in synaptic distribution, there is evidence that qualitative differences in excitatory to inhibitory balance also exist in the pathways conveying input from cutaneous afferents and rubrospinal systems to triceps surae motoneurones. These qualitative differences are correlated with the motor unit twitch type. © 1970 The Physiological Society
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| 27. |
- Cabaj, Anna, et al.
(författare)
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Same spinal interneurons mediate reflex actions of group Ib and group II afferents and crossed reticulospinal actions.
- 2006
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 95:6, s. 3911-22
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to analyze interactions between neuronal networks mediating centrally initiated movements and reflex reactions evoked by peripheral afferents; specifically whether interneurons in pathways from group Ib afferents and from group II muscle afferents mediate actions of reticulospinal neurons on spinal motoneurons by contralaterally located commissural interneurons. To this end reticulospinal tract fibers were stimulated in the contralateral medial longitudinal fascicle (MLF) in chloralose-anesthetized cats in which the ipsilateral half of the spinal cord was transected rostral to the lumbosacral enlargement. In the majority of interneurons mediating reflex actions of group Ib and group II afferents, MLF stimuli evoked either excitatory or inhibitory postsynaptic potentials (EPSPs and IPSPs, respectively) or both EPSPs and IPSPs attributable to disynaptic actions by commissural interneurons. In addition, in some interneurons EPSPs were evoked at latencies compatible with monosynaptic actions of crossed axon collaterals of MLF fibers. Intracellular records from motoneurons demonstrated that both excitation and inhibition from group Ib and group II afferents are modulated by contralaterally descending reticulospinal neurons. The results lead to the conclusion that commissural interneurons activated by reticulospinal neurons affect motoneurons not only directly, but also by enhancing or weakening activation of premotor interneurons in pathways from group Ib and group II afferents. The results also show that both excitatory and inhibitory premotor interneurons are affected in this way and that commissural interneurons may assist in the selection of reflex actions of group Ib and group II afferents during centrally initiated movements.
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| 28. |
- Cavallari, P., et al.
(författare)
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Post‐synaptic actions of midlumbar interneurones on motoneurones of hind‐limb muscles in the cat.
- 1987
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 389, s. 675-689
-
Tidskriftsartikel (refereegranskat)abstract
- 1. The hypothesis that interneurones in the 4th lumbar segment (L4) are interposed between group I and group II afferents and hind‐limb motoneurones has been tested. Action potentials of single interneurones were induced by ionophoretically applied homocysteate and recorded in parallel with post‐synaptic potentials in motoneurones; the latter were recorded from motor axons in the ventral root of the first sacral segment as population potentials, using the sucrose gap technique. 2. The action potentials of twenty‐four L4 interneurones were found to be followed by either e.p.s.p.s. or i.p.s.p.s in motoneurones. The latencies of the majority of these p.s.p.s were consistent with monosynaptically evoked excitation or inhibition of motoneurones since they exceeded the latencies of antidromic activation of the interneurones from the S1 motor nuclei by only a fraction of a millisecond. 3. The dominant input to both the excitatory and the inhibitory interneurones was from group II muscle afferents, in particular from the quadriceps nerve. The latencies of excitation of the interneurones by these afferents indicated a monosynaptic coupling between them. The same interneurones were co‐excited by group I and cutaneous afferents and by descending fibres. 4. We conclude that not only excitation but also inhibition of hind‐limb motoneurones from group II afferents may be mediated disynaptically and that interneurones in the 4th lumbar segment contribute to both. © 1987 The Physiological Society
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| 29. |
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| 30. |
- Czarkowska, J., et al.
(författare)
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Common interneurones in reflex pathways from group 1a and 1b afferents of knee flexors and extensors in the cat.
- 1981
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 310, s. 367-380
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Tidskriftsartikel (refereegranskat)abstract
- 1. Input from group I afferents of knee flexors and extensors to interneurones in Rexed's laminae V‐VI in the cat spinal cord was analysed by use of intracellular recording and electrical stimulation of the nerves to differentiate between group Ia and Ib synaptic actions. The aim was to find out if these interneurones may mediate synaptic actions of both group Ia and Ib afferents. 2. 28% of the forty‐nine neurones analysed were excited by both group Ia and group Ib afferents; 32% were inhibited by both and 35% were excited by the one and inhibited by the other. Taking into account all of these actions, input from both subgroups of group I afferents was found in nearly 60% of neurones. Most were also excited and/or inhibited by group I afferents of ankle and toe extensors. 3. Selective (excitatory and/or inhibitory) input from Ia afferents was found in 18% and from Ib afferents in 22% of the neurones. 4. Excitation was evoked from Ia afferents of either knee flexors or extensors but not from both. In several of the neurones Ia i.p.s.p.s were, however, evoked from both posterior biceps‐semitendinosus and quadriceps. 5. Intracellular staining with horseradish peroxidase revealed axonal projections of laminae V‐VI interneurones to motor nuclei as well as to the intermediate zone, ipsilateral as well as contralateral. No correlation was found between patterns of input from group I afferents and axonal projections, and interneurones co‐excited by Ia and Ib afferents were among these with different axonal projections. © 1981 The Physiological Society
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| 31. |
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| 32. |
- Djouhri, L, et al.
(författare)
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Indications for coupling between feline spinocervical tract neurones and midlumbar interneurones.
- 1998
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Ingår i: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. - 0014-4819. ; 119:1, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of collateral segmental actions of spinocervical tract (SCT) neurones upon interneurones with input from cutaneous and group II muscle afferents was investigated in deeply anaesthetized cats. To this end, intracellular and/or extracellular recordings were made from 35 dorsal horn and 15 intermediate zone interneurones in midlumbar segments of the spinal cord and effects of stimulation of the ipsilateral dorso-lateral funiculus (DLF) at C3 and C1 levels, i.e. below and above the lateral cervical nucleus where axons of SCT cells terminate, were compared. The stimuli applied at the C3 segment were within the range of stimuli (50-100 microA) required for antidromic activation of SCT neurones in the same experiment. Those applied at the C segment (200-500 microA) were at least 3 times stronger than C3 stimuli. Under the same experimental conditions, long ascending and descending tract neurones (dorsal spino-cerebellar and rubro-spinal tract neurones) with axons in the DLF were activated at similar thresholds from the C and C3 segments. Intracellular recordings were made from 29 interneurones of which 19 (65%) were dorsal horn and 10 (35%) were intermediate zone interneurones. Excitatory postsynaptic potentials (EPSPs) evoked by single stimuli applied at the C3 segment, but not the C segment, were found in 14 (48%) of those interneurones; their latencies (3.0-5.7 ms) and frequency following with only minimal temporal facilitation were as required for potentials being evoked monosynaptically by the fastest conducting SCT neurones. Extracellular recordings were made from 30 interneurones (24 dorsal horn and 6 intermediate zone interneurones), and in these neurones spike potentials induced from the C3, but not from the C segment, were evoked only by short trains of stimuli. However, their latencies from the first effective stimulus (4.3-5.4 ms) were compatible with mono- or oligosynaptically mediated collateral actions of SCT neurones. They were found in 10 (33%) of the 30 investigated interneurones. Similar effects of C3 stimuli were found in similar proportions of dorsal horn interneurones and intermediate zone interneurones. Indications were also found for synaptic actions evoked by C3 stimuli that could not be attributed to direct collateral actions of SCT neurones. In some intracellularly recorded dorsal horn interneurones, short-latency EPSPs were evoked from the C3 segment by the 2nd or 3rd stimulus in the train, but not by single stimuli. In other dorsal horn and intermediate zone interneurones, inhibitory postsynaptic potentials (IPSPs) were evoked from the C3 segment at minimal latencies (2.7-3.2 ms), which might be too short to allow their mediation via SCT neurones. We conclude that SCT neurones might be used to forward information from muscle group II and cutaneous afferents not only to neurones in the lateral cervical nucleus and via them to thalamus and cerebral cortex but also to interneurones in spinal reflex pathways. Thereby reflex actions evoked from group II and cutaneous afferents might be co-ordinated with responses mediated by supraspinal neurones. We conclude also that dorsal horn and intermediate zone mid-lumbar interneurones might contribute to the previously reported di-and poly-synaptic excitation or inhibition of postsynaptic dorsal column (PSDC), spinothalamic tract (STT) and spinomesencephalic tract (SMT) neurones by collateral actions of SCT cells. Thereby these interneurones might contribute to the co-ordination of responses mediated by various populations of supraspinal neurones.
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| 33. |
- Dougherty, Kimberly J, et al.
(författare)
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Membrane receptors involved in modulation of responses of spinal dorsal horn interneurons evoked by feline group II muscle afferents.
- 2005
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 25:3, s. 584-93
-
Tidskriftsartikel (refereegranskat)abstract
- Modulatory actions of a metabotropic 5-HT1A&7 membrane receptor agonist and antagonist [(+/-)-8-hydroxy-2-(di-n-propylamino)-tetralin; N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane-carboxamide] and an ionotropic 5-HT3 membrane receptor agonist and antagonist [2-methyl-serotonin (2-Me 5-HT); N-(1-azabicyclo[2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-8-carboxamide hydrochloride] were investigated on dorsal horn interneurons mediating reflex actions of group II muscle afferents. All drugs were applied ionophoretically in deeply anesthetized cats. Effects of agonists were tested on extracellularly recorded responses of individual interneurons evoked by electrical stimulation of group II afferents in a muscle nerve. Effects of antagonists were tested against the depression of these responses after stimulation of raphe nuclei. The results show that both 5-HT1A&7 and 5-HT3 membrane receptors are involved in counteracting the activation of dorsal horn interneurons by group II afferents. Because only quantitative differences were found within the sample of the tested neurons, these results suggest that modulatory actions of 5-HT on excitatory and inhibitory interneurons might be similar. The relationship between 5-HT axons and axons immunoreactive for the 5-HT3A receptor subunit, which contact dorsal horn interneurons, was analyzed using immunofluorescence and confocal microscopy. Contacts from both types of axons were found on all interneurons, but their distribution and density varied, and there was no obvious relationship between them. In two of six interneurons, 5-HT3A-immunoreactive axons formed ring-like arrangements around the cell bodies. In previous studies, axons possessing 5-HT3 receptors were found to be excitatory, and as 2-Me 5-HT depressed transmission to dorsal horn interneurons, the results indicate that 5-HT operates at 5-HT3 receptors presynaptic to these neurons to depress excitatory transmission.
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| 34. |
- Edgley, S. A., et al.
(författare)
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An interneuronal relay for group I and II muscle afferents in the midlumbar segments of the cat spinal cord.
- 1987
-
Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 389, s. 647-674
-
Tidskriftsartikel (refereegranskat)abstract
- 1. The properties of interneurones located in the 4th lumbar segment of the cat spinal cord (L4 interneurones) have been investigated by intracellular and extracellular recording from individual neurones. The study focused on interneurones projecting to hind‐limb motor nuclei and/or interposed in pathways from group II muscle afferents. The projection to motor nuclei was assessed from antidromic activation of the neurones by stimuli applied in the motor nuclei of the 7th lumbar (L7) segment. 2. Interneurones which projected to gastrocnemius‐soleus or hamstring motor nuclei were found in laminae VI and VII and at the border between laminae VII and VIII. The dominant peripheral input to most of them was from group II muscle afferents, but they were also influenced by group I muscle afferents and by afferents in cutaneous, joint and interosseous nerves. Both excitatory post‐synaptic potentials (e.p.s.p.s) and inhibitory post‐synaptic potentials (i.p.s.p.s) were evoked from all of these fibre systems. 3. The same kind of multimodal input was also found in other interneurones in laminae VI and VII. However, their axonal projections were not identified and they might have included neurones projecting to motor nuclei (though outside the areas which were stimulated) as well as neurones with more local actions. 4. Interneurones located in laminae IV and V of the dorsal horn appeared to constitute a separate functional population since both their projections and their input differed from those of the more ventrally located interneurones; none of the dorsal horn interneurones were found to project to motor nuclei and none had input from group I afferents, although they were influenced by group II muscle afferents and by afferents in cutaneous, joint and interosseous nerves. 5. Many of the excitatory actions from group I and II afferents upon L4 interneurones were found to be evoked monosynaptically. A high proportion of L4 neurones synapsing upon motoneurones would thus be interposed in disynaptic reflex pathways from these afferents. In comparison to actions evoked via interneurones of the caudal lumbar segments, any post‐synaptic potentials (p.s.p.s) evoked via L4 interneurones would be delayed. These delays would amount to 0.4‐0.9 ms for p.s.p.s. from group I afferents and by 0.5‐2.5 ms for group II p.s.p.s. 6. In many interneurones, particularly those located ventrally, i.p.s.p.s. were evoked by group I and II muscle afferents at latencies which indicated that they were evoked disynaptically. They may therefore reflect inhibitory interactions between subpopulations of L4 interneurones.(ABSTRACT TRUNCATED AT 400 WORDS) © 1987 The Physiological Society
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| 35. |
- Edgley, S A, et al.
(författare)
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Both dorsal horn and lamina VIII interneurones contribute to crossed reflexes from feline group II muscle afferents.
- 2003
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 552:Pt 3, s. 961-74
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have demonstrated that group II muscle afferents exert powerful actions on contralateral motoneurones and that these actions are mediated primarily via lamina VIII commissural interneurones. We examined whether dorsal horn interneurones also contribute to these actions, as they have been shown to contribute to the actions of group II afferents on ipsilateral motoneurones. We tested the susceptibility of IPSPs and EPSPs evoked from group II afferents in contralateral motoneurones to presynaptic inhibition as an indicator of the relative contribution of dorsal horn interneurones to these PSPs, since the monosynaptic activation of dorsal horn interneurones is more weakly and more briefly depressed by presynaptic inhibition than is the monosynaptic activation of lamina VIII and other intermediate zone and ventral horn interneurones. While the earliest components of IPSPs and EPSPs evoked by group II afferents were abolished by conditioning stimulation of group II afferents, consistent with them being evoked disynaptically by commissural interneurones, trisynaptic components of these PSPs were only partly reduced and are therefore attributed to dorsal horn interneurones. The same conditioning stimuli depressed the disynaptic excitation of lamina VIII commissural interneurones by group II afferents much less effectively than they depressed monosynaptic excitation, indicating that dorsal horn interneurones contribute to this disynaptic excitation. On the basis of these observations we conclude that that dorsal horn interneurones contribute to the late actions of group II muscle afferents on contralateral motoneurones through their disynaptic actions on commissural interneurones.
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| 36. |
- Edgley, S. A., et al.
(författare)
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Evidence that mid‐lumbar neurones in reflex pathways from group II afferents are involved in locomotion in the cat.
- 1988
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 403, s. 57-71
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Tidskriftsartikel (refereegranskat)abstract
- 1. A group of interneurons in the mid‐lumbar segments of the cat spinal cord which mediate disynaptic excitation or inhibition of motoneurones from group II muscle afferents have recently been described. To test the possibility that the activity of these interneurones is related to the activity in the neuronal networks which subserve locomotion we have investigated whether they are influenced by two procedures which can induce locomotion. These procedures were electrical stimulation within the cuneiform nucleus (the ‘mesencephalic locomotor region’) in anaesthetized preparations and systemic administration of 3,4‐dihydroxyphenylalanine (DOPA) in decerebrate, spinalized, unanaesthetized preparations. The interneurones we have tested were located in the fourth lumbar (L4) segment and were excited by group II muscle afferents; more than half of them were antidromically activated from the hindlimb motor nuclei. 2. Stimuli applied in the cuneiform nucleus evoked excitatory postsynaptic potentials (EPSPs) in a high proportion of these interneurones. The stimuli also evoked distinct extracellular field potentials in the ventral horn of the L4 segment. The properties and latencies of both the intra‐ and extracellularly recorded potentials show that they were evoked disynaptically, via supraspinally located relay neurones and a fast‐conducting descending tract. 3. Stimulation of the cortico‐ and rubrospinal tracts excited or inhibited some of the L4 neurones, often at latencies suggesting mono‐ or disynaptic coupling. The neurones which appeared to be monosynaptically excited from the cortico‐ and rubrospinal tracts tended to be located dorsal to the neurones which were activated from the cuneiform nucleus. 4. Systemic administration of DOPA depressed the responses evoked by stimulation of group II afferents of L4 interneurones which projected to motor nuclei. DOPA also depressed extracellular field potentials evoked by group II afferents in the intermediate zone and in the ventral horn (at the location of the interneurones) but hardly affected those in the dorsal horn. 5. By showing that both stimulation in the cuneiform nucleus and the administration of DOPA influence activity of L4 interneurones which are excited by group II afferents and which project to motor nuclei, the results of this study support the hypothesis that these neurones are in some way involved in locomotion. However, the opposing effects of DOPA administration and of stimulation in the cuneiform nucleus make the interpretation of their role in locomotion rather difficult before it is known to what extent they are active throughout the step cycle. © 1988 The Physiological Society
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| 37. |
- Edgley, S. A., et al.
(författare)
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Field potentials generated by group II muscle afferents in the middle lumbar segments of the cat spinal cord.
- 1987
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 385, s. 393-413
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Tidskriftsartikel (refereegranskat)abstract
- 1. A powerful projection from group II muscle afferents of hind‐limb muscles to the 3rd, 4th and 5th segments of the lumbar spinal cord has been demonstrated by focal synaptic field potential recording. 2. Field potentials were found at two locations: one in the dorsal horn (Rexed's laminae IV and V) and the other in the intermediate zone and ventral horn (Rexed's laminae VII and VIII). In the dorsal horn the field potentials were exceptionally large and were evoked only by group II afferents. At more ventral locations, they were smaller and were sometimes preceded by small field potentials evoked by group I afferents. 3. At both locations field potentials could be evoked by stimulation of a number of hind‐limb muscle nerves at strengths sufficient to activate group II afferents. However, some nerves consistently evoked more powerful effects than others and the largest potentials were from the nerves to quadriceps, sartorius and to the pretibial flexor muscles (tibialis anterior and extensor digitorum longus). Activation of articular afferents (from the knee joint nerve) or Pacinian corpuscle afferents (from the interosseous nerve) evoked small field potentials at some locations. 4. In the dorsal horn the latency of the field potentials was so short that they must have been generated monosynaptically. Field potentials in the ventral horn had longer latencies, by 0.5‐1.0 ms, but they also appear to have been monosynaptically evoked by slowly conducting intraspinal collaterals. This conclusion is based primarily on the effects of intraspinal stimulation which was found to antidromically activate afferents with the appropriate latencies and thresholds. 5. Evidence is presented that the dorsal and ventral field potentials are generated by afferents whose receptors can be activated by small (less than 100 micron) muscle stretches. © 1987 The Physiological Society
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| 38. |
- Edgley, S. A., et al.
(författare)
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Information processed by dorsal horn spinocerebellar tract neurones in the cat.
- 1988
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 397, s. 81-97
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Tidskriftsartikel (refereegranskat)abstract
- 1. A group of spinocerebellar tract neurones located in the dorsal horn of the mid‐lumbar segments of the spinal cord but outside of Clarke's column have been investigated by intracellular and extracellular recording from their somata. The existence of these neurones has been demonstrated previously using anatomical methods, but their properties have not been investigated in detail. In contrast to the cells of Clarke's column, these neurones were found to process information from both exteroceptors and proprioceptors. 2. All of the investigated neurones were powerfully excited following stimulation of muscle nerves at strengths sufficient to activate group II afferents while there was no evidence for actions from group I afferents onto any of them. Most were excited by group II afferents from many different nerves, including those from muscles acting on different joints. The latencies and properties of the excitatory postsynaptic potentials (EPSPs) suggest that at least a large proportion of them were monosynaptically evoked. 3. All of the neurones were powerfully excited following electrical stimulation of cutaneous afferents. The most potent effects were evoked from the saphenous and sural nerves which innervate the skin of the leg and thigh. In many cases these EPSPs had latencies indicative of a monosynaptic connection. The superficial peroneal and tibial nerves which innervate the skin of the foot evoked EPSPs which were usually smaller and of longer latency. 4. Responses to adequate stimulation of cutaneous afferents were examined in twenty extracellularly recorded neurones. All but one of them could be discharged by weak mechanical stimulation of the skin over the proximal part of the leg and thigh. None were activated from the skin of the foot. 5. Some of the neurones were influenced by stimulation of the posterior knee joint or interosseous nerves. These actions were relatively weak, however, suggesting that the powerful effects seen on stimulation of muscle nerves were unlikely to have been mediated by articular or Pacinian afferents which contaminate them. 6. Excitation from group II afferents was sometimes followed by inhibition (in 27% of the neurones). In almost all cases the inhibitory postsynaptic potentials (IPSPs) were evoked from the same nerves which evoked EPSPs. The minimal latencies of the IPSPs were approximately 1.0 ms longer than those of the EPSPs, suggesting that they were evoked disynaptically. 7. The possibility that these neurones provide information regarding limb position is discussed. © 1988 The Physiological Society
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| 39. |
- Edgley, S A, et al.
(författare)
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Ipsilateral actions of feline corticospinal tract neurons on limb motoneurons.
- 2004
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 24:36, s. 7804-13
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Tidskriftsartikel (refereegranskat)abstract
- Contralateral pyramidal tract (PT) neurons arising in the primary motor cortex are the major route through which volitional limb movements are controlled. However, the contralateral hemiparesis that follows PT neuron injury on one side may be counteracted by ipsilateral of actions of PT neurons from the undamaged side. To investigate the spinal relays through which PT neurons may influence ipsilateral motoneurons, we analyzed the synaptic actions evoked by stimulation of the ipsilateral pyramid on hindlimb motoneurons after transecting the descending fibers of the contralateral PT at a low thoracic level. The results show that ipsilateral PT neurons can affect limb motoneurons trisynaptically by activating contralaterally descending reticulospinal neurons, which in turn activate spinal commissural interneurons that project back across to motoneurons ipsilateral to the stimulated pyramidal tract. Stimulation of the pyramids alone did not evoke synaptic actions in motoneurons but potently facilitated disynaptic EPSPs and IPSPs evoked by stimulation of reticulospinal tract fibers in the medial longitudinal fascicle. In parallel with this double-crossed pathway, corticospinal neurons could also evoke ipsilateral actions via ipsilateral descending reticulospinal tract fibers, acting through ipsilaterally located spinal interneurons. Because the actions mediated by commissural interneurons were found to be stronger than those of ipsilateral premotor interneurons, the study leads to the conclusion that ipsilateral actions of corticospinal neurons via commissural interneurons may provide a better opportunity for recovery of function in hemiparesis produced by corticospinal tract injury.
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| 40. |
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| 41. |
- Emonet‐Dénand, Françoise, et al.
(författare)
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Skeleto‐fusimotor fibres in the rabbit
- 1970
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 210, s. 669-680
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Tidskriftsartikel (refereegranskat)abstract
- 1. In rabbits, repetitive stimulation of single motor axons to lumbrical muscles elicits both a contraction of extrafusal muscle fibres and an increase in the discharge frequency of spindle primary endings. 2. This activation of the sensory endings can be attributed to the contraction of intrafusal muscle fibres because it persists after the contraction of extrafusal muscle fibres has been suppressed by selective curarization of their neuromuscular junctions. 3. In non‐curarized preparations the frequency of most of the afferent discharges continues to increase when rates of stimulation of motor fibres exceed the tetanic fusion frequency of the extrafusal muscle fibres. 4. The effect of repetitive stimulation of motor fibres that supply extrafusal and intrafusal muscle fibres was studied on the responses of primary endings to phasic stretch. Of twelve fibres, eight were found to exert a dynamic effect and four a static one. 5. Selective curarization of the extrafusal neuromuscular junctions does not modify the nature of the static and dynamic effects. © 1970 The Physiological Society
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| 42. |
- Eriksson, J., et al.
(författare)
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Antispastic effects of L-dopa
- 1996
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Ingår i: Experimental Brain Research. - 0014-4819. ; 111, s. 296-304
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Tidskriftsartikel (refereegranskat)abstract
- Antispastic effects of the noradrenaline and dopamine precursor l-3,4-dihydroxyphelanine (L-dopa) were investigated in 11 subjects in which exaggerated stretch reflexes developed after spinal cord injuries. The effects were evaluated from changes in the electromyographic (EMG) response of the quadriceps muscle during tendon jerks evoked by standardized taps over the patellar tendon, in clonus and in resistance to passive movements of the limb. After administration of L-dopa, EMG responses occurring 30-150 ms after the tendon tap decreased to about 50% of control, and clinical tests revealed a marked decrease in the resistance to muscle stretches and in the degree of clonus. The effects were maximal within about 1 h. The depressive actions of L-dopa are interpreted as being exerted primarily at the spinal level, since they were evoked in paraplegics and tetraplegics. The results support the previous hypothesis that group II muscle afferents contribute to the exaggerated stretch reflex in spastic patients because L-dopa depresses transmission from group II but not from group I muscle afferents. They also indicate the possibility of using L-dopa in the treatment of spastic patients.
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| 43. |
- Fetz, E. E., et al.
(författare)
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Autogenetic inhibition of motoneurones by impulses in group Ia muscle spindle afferents.
- 1979
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 293, s. 173-195
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Tidskriftsartikel (refereegranskat)abstract
- 1. Inhibitory post‐synaptic potentials evoked by adequate stimulation of group Ia muscle spindle afferents of homonymous and synergistic muscles and by selective electrical stimulation of tendon organ afferents were analysed in motoneurones of triceps surae and plantaris. 2. Selective activation of Ia afferents was verified to occur with brief stretches of triceps surae and plantaris 35 micrometer or less in amplitude with an initial muscle tension of 5 N; stretches of 30‐‐35 micrometer were estimated to activate 80‐‐90% of Ia afferents in these muscles. Under the same conditions the lowest thresholds for group Ib tendon organ afferents were about 40 micrometer. 3. Stretches less than or equal to 30 micrometer evoked i.p.s.p.s in 80% of triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s wef triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s were 10 micrometer or less. However, such low thresholds for stretch‐evoked i.p.s.p.s, lower than the thresholds for activation of Ib afferents, were found mainly in spinalized, unanaesthetized (after decerebration) or lightly anaesthetized animals. The latencies of these i.p.s.p.s indicated disynaptic and trisynaptic coupling between Ia afferents and motoneurones. The i.p.s.p.s were evoked (i) from the homonymous and synergistic muscles stretched together, (ii) from the homonymous muscles alone and (iii) from the synergistic muscles alone. 4. Control experiments showed that i.p.s.p.s could be evoked by stretches sub‐threshold for discharging motoneurones, thus showing that those i.p.s.p.s were not mediated by Renshaw cells. The stretch‐evoked i.p.s.p.s disappeared after sectioning the nerves from the corresponding muscles, further excluding their mediation by afferents other than group Ia afferents from thf stretched muscle. 5. In order to selectively activate tendon organ afferents, thresholds for excitation of Ia afferents by electrical stimuli were increased to a level above the threshold for Ib afferents by prolonged muscle vibration (Coppin, Jack & MacLennan, 1970). I.p.s.p.s evoked by stimuli near threshold for Ib afferents appeared with latencies indicating disynaptic coupling. Later (trisynaptic) components of Ib i.p.s.p.s required somewhat stronger stimuli. 6. Amplitudes of Ia i.p.s.p.s evoked by muscle stretches activating about 80% of muscle spindle afferents were compared with amplitudes of Ib i.p.s.p.s due to less than 50% of tendon organ afferents of the same muscles. The Ia i.p.s.p.s were much smaller (16‐‐35%) than the Ib i.p.s.p.s. The amplitudes of such Ia and Ib i.p.s.p.s constituted about 10 and 25‐‐66%, respectively, of the maximal i.p.s.p.s evoked by electrical stimulation of all group I afferents. 7. We conclude that inhibition of motoneurones may be evoked from Ia muscle spindle afferents from homonymous and synergistic muscles as well as from Ib tendon organ afferents... © 1979 The Physiological Society
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| 44. |
- Fu, T. ‐C, et al.
(författare)
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Effects of Volleys in Cortico‐spinal Tract Fibres on Ventral Spino‐cerebellar Tract Cells in the Cat
- 1977
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 100, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Both excitation and inhibition has been found in cells of origin of the ventral spino‐cerebellar tract (VSCT) to be evoked by volleys in cortico‐spinal fibres. The earliest EPSPs and IPSPs had features of disynaptically evoked postsynaptic potentials; these were, however, found only in a small proportion of cells and polysynaptic EPSPs and IPSPs were dominating. Postsynaptic potentials evoked in VSCT cells from primary afferents were effectively facilitated by cortico‐spinal volleys. The cortico‐spinal effects on VSCT cells may thus well be mediated by the same interneurones which mediate their excitation or inhibition from the periphery and which could evoke similar postsynaptic potentials in motoneurones. Generally all the observations are in keeping with the hypothesis (Lundberg 1971) that VSCT cells monitor transmission through interneurones interposed in various reflex paths to motoneurones. © 1977 Scandinavian Physiological Society
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| 45. |
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| 46. |
- Galea, Mary Pauline, et al.
(författare)
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Bilateral postsynaptic actions of pyramidal tract and reticulospinal neurons on feline erector spinae motoneurons.
- 2010
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Ingår i: The Journal of neuroscience. - 1529-2401. ; 30:3, s. 858-869
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Tidskriftsartikel (refereegranskat)abstract
- Trunk muscles are important for postural adjustments associated with voluntary movements but little has been done to analyze mechanisms of supraspinal control of these muscles at a cellular level. The present study therefore aimed to investigate the input from pyramidal tract (PT) neurons to motoneurons of the musculus longissimus lumborum of the erector spinae and to analyze to what extent it is relayed by reticulospinal (RS) neurons. Intracellular records from motoneurons were used to evaluate effects of electrical stimulation of medullary pyramids and of axons of RS neurons descending in the medial longitudinal fasciculus (MLF). The results revealed that similar synaptic actions were evoked from the ipsilateral and contralateral PTs, including disynaptic and trisynaptic EPSPs and trisynaptic IPSPs. Stimulation of the MLF-evoked monosynaptic and disynaptic EPSPs and disynaptic or trisynaptic IPSPs in the same motoneurons. All short-latency PSPs of PT origin were abolished by transection of the MLF, while they remained after transection of PT fibers at a spinal level. Hence, RS neurons might serve as the main relay neurons of the most direct PT actions on musculus (m.) longissimus. However, longer-latency IPSPs remaining after MLF or PT spinal lesions and after ipsilateral or contralateral hemisection of spinal cord indicate that PT actions are also mediated by ipsilaterally and/or contralaterally located spinal interneurons. The bilateral effects of PT stimulation thereby provide an explanation why trunk movements after unilateral injuries of PT neurons (e.g., stroke) are impaired to a lesser degree than movements of the extremities.
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| 47. |
- Geborek, Pierre, et al.
(författare)
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A survey of spinal collateral actions of feline ventral spinocerebellar tract neurons
- 2013
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 37:3, s. 380-392
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to identify spinal target cells of spinocerebellar neurons, in particular the ventral spinocerebellar tract (VSCT) neurons, giving off axon collaterals terminating within the lumbosacral enlargement. Axons of spinocerebellar neurons were stimulated within the cerebellum while searching for most direct synaptic actions on intracellularly recorded hindlimb motoneurons and interneurons. In motoneurons the dominating effects were inhibitory [inhibitory postsynaptic potentials (IPSPs) in 67% and excitatory postsynaptic potentials (EPSPs) in 17% of motoneurons]. Latencies of most IPSPs indicated that they were evoked disynaptically and mutual facilitation between these IPSPs and disynaptic IPSPs evoked by group Ia afferents from antagonist muscles and group Ib and II afferents from synergists indicated that they were relayed by premotor interneurons in reflex pathways from muscle afferents. Monosynaptic EPSPs from the cerebellum were accordingly found in Ia inhibitory interneurons and intermediate zone interneurons with input from group I and II afferents but only oligosynaptic EPSPs in motoneurons. Monosynaptic EPSPs following cerebellar stimulation were also found in some VSCT neurons, indicating coupling between various spinocerebellar neurons. The results are in keeping with the previously demonstrated projections of VSCT neurons to the contralateral ventral horn, showing that VSCT neurons might contribute to motor control at a spinal level. They might thus play a role in modulating spinal activity in advance of any control exerted via the cerebellar loop.
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| 48. |
- Gladden, M H, et al.
(författare)
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Coupling between serotoninergic and noradrenergic neurones and gamma-motoneurones in the cat.
- 2000
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Ingår i: The Journal of physiology. - 0022-3751. ; 527 Pt 2, s. 213-23
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Tidskriftsartikel (refereegranskat)abstract
- Noradrenaline is known to suppress transmission from group II muscle afferents when locally applied to gamma-motoneurones, and serotonin (5-HT) facilitates the transmission. The purpose of this investigation was to search for evidence of monoaminergic innervation of gamma-motoneurones. Eight gamma-motoneurones were labelled with rhodamine-dextran, and 50 micrometer thick sagittal sections of the spinal cord containing them were exposed to antibodies against dopamine beta-hydroxylase (DBH) and 5-HT. All the cells were directly and/or indirectly excited by muscle group II afferents from the muscle they innervated and/or other muscles. Appositions between monoaminergic fibres and the labelled somata and dendrites were located with three-colour confocal laser scanning microscopy by examining series of optical sections at 1 or 0.5 micrometer intervals. DBH and 5-HT varicosities formed appositions with the somata and dendrites of all the gamma-motoneurones. The mean packing densities for 5-HT (1.12 +/- 0.11 appositions per 100 micrometer(2) for somata and 0.91 +/- 0.07 per 100 micrometer(2) for dendrites) were similar to the densities of contacts reported for alpha-motoneurones. Monoaminergic varicosities in apposition to dendrites greatly outnumbered those on the somata. The density of DBH appositions was consistently lower - corresponding means were 53% and 62% of those for 5-HT on the somata and dendrites, respectively. It is concluded from an analysis of the distribution and density of varicosities in apposition to the gamma-motoneurones compared with the density in the immediate surround of the dendrites that there is indeed both a serotoninergic and noradrenergic innervation of gamma-motoneurones.
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| 49. |
- Gladden, M. H., et al.
(författare)
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Coupling between serotoninergic and noradrenergic neurones and γ-motoneurones in the cat
- 2000
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 527, s. 213-223
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Tidskriftsartikel (refereegranskat)abstract
- 1. Noradrenaline is known to suppress transmission from group II muscle afferents when locally applied to γ-motoneurones, and serotonin (5-HT) facilitates the transmission. The purpose of this investigation was to search for evidence of monoaminergic innervation of γ-motoneurones. 2. Eight γ-motoneurones were labelled with rhodamine-dextran, and 50 μm thick sagittal sections of the spinal cord containing them were exposed to antibodies against dopamine β-hydroxylase (DBH) and 5-HT. All the cells were directly and/or indirectly excited by muscle group II afferents from the muscle they innervated and/or other muscles. 3. Appositions between monoaminergic fibres and the labelled somata and dendrites were located with three-colour confocal laser scanning microscopy by examining series of optical sections at 1 or 0·5 μm intervals. 4. DBH and 5-HT varicosities formed appositions with the somata and dendrites of all the γ-motoneurones. The mean packing densities for 5-HT (1·12 ± 0·11 appositions per 100 μm2 for somata and 0·91 ± 0·07 per 100 μm2 for dendrites) were similar to the densities of contacts reported for α-motoneurones. Monoaminergic varicosities in apposition to dendrites greatly outnumbered those on the somata. 5. The density of DBH appositions was consistently lower - corresponding means were 53% and 62% of those for 5-HT on the somata and dendrites, respectively. 6. It is concluded from an analysis of the distribution and density of varicosities in apposition to the γ-motoneurones compared with the density in the immediate surround of the dendrites that there is indeed both a serotoninergic and noradrenergic innervation of γ-motoneurones.
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| 50. |
- Gladden, M H, et al.
(författare)
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New observations on coupling between group II muscle afferents and feline gamma-motoneurones.
- 1998
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Ingår i: The Journal of physiology. - 0022-3751. ; 512 ( Pt 2), s. 507-20
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Tidskriftsartikel (refereegranskat)abstract
- 1. Extra- or intracellular recordings were made from seventy-six gamma-motoneurones of hindlimb muscles in chloralose anaesthetized cats to re-assess the coupling between secondary muscle spindle afferents (group II muscle afferents) and these neurones. The latencies of a number of responses evoked by group II muscle afferents in gamma-motoneurones were shorter than minimal latencies of responses induced disynaptically in other spinal neurones. These latencies are therefore compatible with monosynaptic coupling between muscle spindle secondaries and gamma-motoneurones. 2. Responses fulfilling criteria for monosynaptically evoked responses were seen in about one third of gamma-motoneurones with input from the group II muscle afferents tested (in 6 of 18 motoneurones recorded intracellularly and in 26 of 74 motoneurones recorded extracellularly). They were usually evoked from only one of the stimulated nerves, stimulation of group II afferents of other nerves being followed by responses at longer latencies. 3. Most gamma-motoneurones were excited by group II afferents from several muscles, both flexors and extensors. However, a comparison of group II input to gamma-motoneurones innervating medial gastrocnemius and four other hindlimb muscles revealed differences in both incidence and sources. 4. This study extends results of previous studies by providing evidence that some synaptic actions of group II afferents, including afferents from the same muscle, are evoked monosynaptically, and may assist in sustaining the activation of gamma-motoneurones by positive feedback.
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