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| 2. |
- 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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| 3. |
- 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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| 4. |
- Hongo, T., et al.
(författare)
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Convergence of excitatory and inhibitory action on interneurones in the lumbosacral cord
- 1966
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 1, s. 338-358
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Tidskriftsartikel (refereegranskat)abstract
- Intracellular recording has been made in spinal cats from more than 100 interneurones in the dorsal horn and intermediary region of the lumbosacral spinal cord. The majority of interneurones receive not only EPSPs but also IPSPs from primary afferents. The IPSPs are evoked from three different systems, group I muscle afferents (probably Ib), low threshold cutaneous afferents and the FRA. The shortest central latency of the IPSPs indicates a disynaptic linkage from primary afferents. Interneurones with monosynaptic EPSPs from group I muscle afferents may receive IPSPs from all the above mentioned afferent systems. Interneurones with monosynaptic EPSPs from cutaneous afferents receive their inhibition from the two latter afferent systems. Convergence of EPSPs and IPSPs from the FRA may occur on the same interneurone. The results are discussed mainly with respect to inhibitory interaction between spinal reflex pathways. © 1966 Springer-Verlag.
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| 5. |
- Hongo, T., et al.
(författare)
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Effects from the sensorimotor cortex on the spinal cord in cats with transected pyramids
- 1967
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 3, s. 117-134
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Tidskriftsartikel (refereegranskat)abstract
- Effects of stimulation of the sensorimotor cortex on activity of the lumbosacral cord were studied in pyramidotomized cats. The following actions initiated by corticofugal volleys were found: 1. postsynaptic effects on motoneurones, mainly excitatory in flexor motoneurones and inhibitory or excitatory in extensor motoneurones, 2. facilitation of spinal reflexes to motoneurones at an interneuronal level, 3. depolarization of presynaptic terminals of group Ib and cutaneous fibres. The latencies of the earliest cortical effects on motoneurones as indicated by modification of monosynaptic reflexes or PSPs were 9-12 msec. Experiments with lesions of different spinal tracts suggest that the effects on motoneurones are mediated mainly by pathways in the ventral part of the lateral funiculus (probably reticulospinal), the facilitation of reflex transmission by pathways in the dorsal part of the lateral funiculus (probably rubrospinal) and primary afferent depolarization by both the former and the latter pathways. The strongest cortical effects were evoked by stimulation of an area around the postcruciate dimple. © 1967 Springer-Verlag.
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| 6. |
- Hongo, T., et al.
(författare)
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Post‐synaptic excitation and inhibition from primary afferents in neurones of the spinocervical tract
- 1968
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 199, s. 569-592
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Tidskriftsartikel (refereegranskat)abstract
- 1. Intra‐ and extracellular recordings were made from cells of the spinocervical tract in the lumbosacral spinal cord. A convergence of monosynaptic excitatory post‐synaptic potentials (EPSPs) and disynaptic inhibitory post‐synaptic potentials (IPSPs) was a general pattern of effects from the low threshold cutaneous fibres. Unitary IPSPs, probably mediated via the same disynaptic path, were evoked by light touch of hairs, which was also the adequate stimulus for exciting the cells. The receptive field for unitary IPSPs was closely related to the excitatory receptive field but was eccentric, not of a surround type. 2. EPSPs, IPSPs, or both, were evoked from the flexor reflex afferents in the great majority of neurones. Disynaptic IPSPs may be evoked from the interosseous nerve. No effects were produced by volleys in group I muscle afferents. 3. It is suggested, on the basis of the spatial organization of the excitatory and inhibitory receptive skin fields, that the spinocervical tract may give information regarding the direction of tactile stimuli. © 1968 The Physiological Society
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| 7. |
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| 8. |
- Hongo, T., et al.
(författare)
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The rubrospinal tract. I. Effects on alpha-motoneurones innervating hindlimb muscles in cats
- 1969
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 7, s. 344-364
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Tidskriftsartikel (refereegranskat)abstract
- 1. The effect of stimulation of the red nucleus on lumbosacral motoneurones was investigated in cats with conditioning of monosynaptic test reflexes and intracellular recording. 2. Experimental procedures were adopted to assure that the effect of stimulation was mediated by the rubrospinal tract. 3. Excitation of flexor and inhibition of extensor motoneurones is common but a mixture of EPSPs and IPSPs is found in many motoneurones. In some extensor (particularly toe extensor) motor nuclei there is dominating excitation. 4. Differential effects are found in motor nuclei innervating fast and slow muscles, excitation being more prevalent in the former and inhibition in the latter. 5. For both EPSPs and IPSPs the minimal synaptic linkage is disynaptic but in one exceptional case a monosynaptic EPSP was observed. 6. The results are discussed in relation to other findings regarding the interneuronal organization in the spinal cord. © 1969 Springer Verlag.
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| 9. |
- Hongo, T., et al.
(författare)
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The rubrospinal tract. II. Facilitation of interneuronal transmission in reflex paths to motoneurones
- 1969
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 7, s. 365-391
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Tidskriftsartikel (refereegranskat)abstract
- 1. The effect of stimulation of the red nucleus on transmission of synaptic actions from different systems of primary afferents to alpha motoneurones has been investigated in cats, mainly with intracellular recording from motoneurones. 2. The dominating effect is facilitation, presumably caused by excitatory action exerted from the rubrospinal tract on interneurones of reflex arcs. The time course of facilitation suggests that the minimal linkage from the rubrospinal tract to these interneurones is monosynaptic. 3. Interneuronal transmission in reflex pathways from the following afferent systems is facilitated: a) Ia inhibitory between flexors and extensors. Rubrospinal facilitation did not reveal Ia inhibitory pathways between adductors and abductors at the hip. b) Ib excitatory and inhibitory. There is marked facilitation of the reciprocal effects evoked by Ib afferents from extensors but also of other Ib pathways, for example inhibitory from extensors to flexor nuclei and from flexors to extensor nuclei and excitatory from flexors to extensor nuclei. c) Low threshold joint, inhibitory and excitatory, presumably from afferents with Ruffini endings. d) Low threshold cutaneous, excitatory and inhibitory. Since transmission from these afferents could be facilitated under conditions when there was no effect on transmission from high threshold muscle afferents it is postulated that the effect is exerted on pathways which are not part of the common pathways from the flexor reflex afferents. e) Plexor reflex afferents, excitatory and inhibitory. Facilitation of these pathways is not found regularly, in some cases there was no effect and in others inhibition. 4. The effects are discussed in relation to the complex effects evoked from the rubrospinal tract in motoneurones and to supraspinal regulation of proprioceptive reflexes. 5. It is postulated that in complex movements alternative Ib patterns may be mobilized, whereas flexion-extension movements are subserved by the Ib pattern found in the spinal cat. 6. Facilitation of the Ia inhibitory pathway is taken to indicate "α-γ-linkage" in reciprocal inhibition. It is pointed out that convergence from Ia and descending impulses on a common inhibitory interneurone may play an important role in the regulation of α-γ-linked flexion-extension movements. © 1969 Springer Verlag.
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| 10. |
- Hongo, T., et al.
(författare)
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The rubrospinal tract. III. Effects on primary afferent terminals
- 1972
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 15, s. 39-53
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Tidskriftsartikel (refereegranskat)abstract
- 1. Effects evoked by stimulation of the red nucleus on primary afferent terminals in the lower lumbar segments of cats have been investigated by recording dorsal root potentials (DRPs) and by recording (intracellularly and by excitability measurements) the primary afferent depolarization (PAD) evoked in terminals of different afferent systems. Control experiments suggest that the effects are mediated by the rubrospinal tract. 2. Stimulation of the red nucleus evoked a large DRP and correspondingly there was a pronounced PAD in Ib and low threshold cutaneous afferents. A dual effect was found in Ia afferent terminals; sometimes a weak PAD was detected while in other cases there was dominating primary afferent hyperpolarization (PAH). 3. Rubrospinal volleys are found to facilitate transmission of DRPs evoked from Ia, Ib, cutaneous and high threshold muscle afferents, presumably by exerting an excitatory action on the interneurones mediating the effect from these afferents. Stimulation of the red nucleus may also inhibit transmission in the pathway mediating depolarization of Ia afferent terminals from Ia afferents, probably by activating a segmental pathway from the flexor reflex afferents from which the same effect is evoked. It is postulated that the PAH evoked in Ia afferents from the red nucleus is due to this inhibitory effect and caused by a removal of a tonic PAD in them. 4. The possible role in motor regulation of the rubral effects on primary afferent terminals is discussed in relation to the rubrospinal effects on reflex pathways to motoneurones. This work was supported by the Swedish Medical Research Council (Project No. 14X-94-07C). © 1972 Springer-Verlag.
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