| 1. |
- Jankowska, Elzbieta, et al.
(författare)
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Contacts between serotoninergic fibres and dorsal horn spinocerebellar tract neurons in the cat and rat: A confocal microscopic study
- 1995
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Ingår i: Neuroscience. - 0306-4522. ; 67, s. 477-487
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Tidskriftsartikel (refereegranskat)abstract
- Contacts between serotoninergic nerve fibres and dorsal horn dorsal spinocerebellar tract neurons were analysed in order to investigate the morphological basis of actions of serotonin upon dorsal spinocerebellar tract neurons. In a series of experiments dorsal spinocerebellar tract neurons were labelled with intracellularly injected rhodamine-dextran in the cat. The neurons were monosynaptically excited by group II muscle afferents and cutaneous afferents and were identified by antidromic activation following stimuli applied in the cerebellum. In the second series of experiments dorsal spinocerebellar tract neurons were labelled by retrograde transport of Fluorogold injected into the cerebellum in the rat. In both series, serotoninergic fibres were labelled by using a specific anti-serotonin antiserum and were revealed by immunofluorescence. Appositions between the serotoninergic fibres and the cells were inspected with a dual channel confocal microscope. The merged images obtained with the two channels of the microscope were viewed in single optical planes 2 μm apart and in rotated three-dimensional reconstructions. Serotoninergic nerve fibres were found in apposition to cell bodies of all feline dorsal spinocerebellar tract neurons (n = 7) and of 75% of rat dorsal spinocerebellar tract neurons (n = 90). The numbers of putative contacts on cell bodies varied between less than 100 and nearly 300 (mean 160) in the cat and between about five and 30 in the rat. Contacts with dendrites of feline neurons were seen on 96% of 72 dendrites within 300 μm from soma and on 91% of 23 dendrites at distances of 300-500 μm. The number of such contacts varied from less than five to 150 on a single dendrite within these ranges of distances. Their total number within 100 μm from the soma was comparable or exceeded the number of contacts on the soma. © 1995 IBRO.
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| 2. |
- 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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| 3. |
- Hammar, Ingela, 1964, et al.
(författare)
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A trans-spinal loop between neurones in the reticular formation and in the cerebellum.
- 2011
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Ingår i: The Journal of physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 589:Pt 3, s. 653-65
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Tidskriftsartikel (refereegranskat)abstract
- Voluntary limb movements are initiated in the brain but the neurones responsible for activating the muscles (motoneurones and interneurones) are located in the spinal cord. The spinal cord also contains neurones that provide the brain, and especially the cerebellum, with continuous information on effects of the descending commands. We show that one population of such neurones provide the cerebellum with information on how likely the brain's commands (mediated by descending reticulospinal neurones) are to be executed as planned, depending on the degree of inhibition of motoneurones. They may therefore play an important role in preventing errors in activation of motoneurones and thereby help the brain to correct its signals to the spinal cord before such errors have been committed.
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| 4. |
- Jankowska, Elzbieta, et al.
(författare)
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Collateral actions of premotor interneurons on ventral spinocerebellar tract neurons in the cat.
- 2010
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 104:4, s. 1872-83
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Tidskriftsartikel (refereegranskat)abstract
- Strong evidence that premotor interneurons provide ventral spinocerebellar tract (VSCT) neurons with feedback information on their actions on motoneurons was previously found for Ia inhibitory interneurons and Renshaw cells, while indications for similar actions of other premotor interneurons were weaker and indirect. Therefore the aim of the present study was to reexamine this possibility with respect to interneurons relaying actions of group Ib afferents from tendon organs and group II afferents from muscle spindles. In all, 133 VSCT neurons in the L3-L5 segments (including 41 spinal border neurons) were recorded from intracellularly in deeply anesthetized cats to verify that stimuli applied in motor nuclei evoked monosynaptic inhibitory postsynaptic potentials (IPSPs) attributable to stimulation of axon collaterals of premotor interneurons. IPSPs were found in over two thirds of the investigated neurons. When intraspinal stimuli were preceded by stimuli applied to a muscle nerve at critical intervals, IPSPs evoked from motor nuclei were considerably reduced, indicating a collision of nerve volleys in axons of interneurons activated by group I and group II afferents. In individual VSCT neurons monosynaptic IPSPs were evoked from both biceps-semitendinosus and gastrocnemius-soleus motor nuclei, in parallel with disynaptic IPSPs from group Ib and group II as well as group Ia afferents. These observations indicate that individual VSCT neurons may monitor the degree of inhibition of both flexor and extensor motoneurons by premotor interneurons in inhibitory pathways from group Ib and group II afferents to motoneurons. They may thus be providing the cerebellum with feedback information on actions of these premotor interneurons on motoneurons.
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| 5. |
- Jankowska, Elzbieta, et al.
(författare)
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Effects of serotonin on dorsal horn dorsal spinocerebellar tract neurons.
- 1995
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Ingår i: Neuroscience. - 0306-4522. ; 67:2, s. 489-95
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Tidskriftsartikel (refereegranskat)abstract
- Effects of ionophoretic application of serotonin and of one of its agonists were tested on responses of dorsal horn dorsal spinocerebellar tract neurons evoked by electrical stimulation of peripheral nerves. Both drugs depressed monosynaptically evoked actions of group II muscle afferents; they decreased the number and/or increased the latency of spike potentials evoked by these afferents. In contrast, synaptic actions of low-threshold cutaneous afferents (mono- or oligosynaptic) were facilitated in the majority of the neurons, as judged by decrease in the latency of spike potentials evoked by stimulation of a cutaneous nerve and/or an increase in the number of these potentials. It is proposed that facilitatory actions assist in maintaining tonic discharges of dorsal spinocerebellar tract neurons in some movements and that the selective control of group II input is used to correlate activity of spinal and supraspinal neurons. Both actions may be subserved by tight contacts between serotoninergic nerve fibres and dorsal spinocerebellar tract neurons, which have been revealed in a parallel study.
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| 6. |
- Jankowska, Elzbieta, et al.
(författare)
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Functional differentiation and organization of feline midlumbar commissural interneurones.
- 2005
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 565:Pt 2, s. 645-58
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Tidskriftsartikel (refereegranskat)abstract
- Interneurones interconnecting the two sides of the spinal cord (commissural interneurones) are critically important for interlimb coordination, but little is known about their organization. We have examined the inputs to commissural interneurones located in the midlumbar segments with projections to contralateral motor nuclei, aiming to determine whether they form distinct subpopulations. Based on intracellular records from 78 interneurones, two major non-overlapping subpopulations were identified: one monosynaptically excited by group II muscle afferents (n=10), the other monosynaptically excited by reticulospinal neurones (n=52). Monosynaptic input from group I muscle afferents and/or from vestibulospinal tract neurones was found in those with monosynaptic reticulospinal, but not group II input, and in a few other neurones (n=6). Only disynaptic input from these sources was found in the remaining 10 interneurones. Disynaptic excitatory input from ipsilateral and contralateral muscle afferents and from descending tracts was distributed less selectively and might mediate coexcitation of interneurones with monosynaptic afferent or descending input. The dominant disynaptic and polysynaptic input was, however, inhibitory. IPSPs were evoked from the descending tracts in a high proportion of the commissural interneurones that were monosynaptically excited by group II afferents (55%) and from group II afferents in a high proportion of the commissural interneurones that were monosynaptically excited by reticulospinal fibres (78%). This distribution suggests that the two subpopulations are activated differentially, rather than being coactivated, in either centrally initiated movements or reflex adjustments. This would be consistent with the previous demonstration that noradrenaline differentially affects commissural neurones of the two subpopulations.
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