| 1. |
- 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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| 2. |
- Harrison, P. J., et al.
(författare)
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An intracellular study of descending and non‐cutaneous afferent input to spinocervical tract neurones in the cat.
- 1984
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 356, s. 245-261
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies of input on to spinocervical tract neurones have been extended by investigating the post‐synaptic actions of non‐cutaneous afferent fibres and of descending tracts on to these neurones, using intracellular recording. In particular, actions of group II muscle, joint and Pacinian afferent fibres and rubro‐ and corticospinal tract fibres were investigated. Group II muscle afferent fibres evoked excitation and inhibition at a minimal latency compatible with a disynaptic linkage. Increasing the stimulus strength to include group III afferent fibres enhanced these post‐synaptic actions only modestly. Inhibition was evoked less frequently and/or required trains of stimuli. Weak stimulation of the interosseous nerve evoked short latency (disynaptic) inhibition or excitation, the latter less frequently. Post‐synaptic potentials evoked below threshold for group III afferent fibres of the interosseous nerve are attributed to the actions of Pacinian corpuscles. Low threshold joint afferent fibres evoked excitation at short latency. Higher threshold joint afferent fibres usually evoked inhibition at longer latency, although high threshold excitation was sometimes observed. Stimulation of the pyramidal tract evoked constant latency, unitary e.p.s.p.s which followed high frequencies. The evidence suggests that such e.p.s.p.s are evoked monosynaptically. Polysynaptic excitation and inhibition were also observed. No convincing evidence could be found of actions evoked directly by the rubrospinal tract, although actions mediated via other descending systems could be induced from the red nucleus. A large degree of convergence was seen from different peripheral and descending systems on to individual neurones. © 1984 The Physiological Society
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| 3. |
- Harrison, P. J., et al.
(författare)
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Do interneurones in lower lumbar segments contribute to the presynaptic depolarization of group I muscle afferents in Clarke's column?
- 1984
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Ingår i: Brain Research. - : Elsevier BV. - 0006-8993. ; 295, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- Intersegmentally evoked primary afferent depolarization (PAD) was analysed to investigate whether any lower lumbar propriospinal neurones are involved in mediating PAD from group I afferents both in the same segments and in Clarke's column. The intersegmental PAD of lower lumbar afferents, as judged by recording dorsal root potentials, was evoked by stimuli applied in the grey matter of L3 and L4 segments. With intraspinal stimuli of 10 μA or less PAD was evoked from two foci: from within the middle part of the dorsal columns and from the dorsal part of the dorsal horn. Dorsal root potentials evoked from the dorsal horn focus appeared with longer latencies. When the dorsal columns were transected PAD was evoked only from the dorsal horn focus. No PAD appeared upon stimulation of Clarke's column after transection of the dorsal column even with stronger (20 μA) stimuli. Interactions between the actions of the intraspinal stimuli and of different groups of afferents were analysed to define the neuronal pathways via which the intersegmental PAD was evoked. Neurones located within both the lower and the upper lumbar segments were found to be involved. Indications have only been found for a contribution of neurones mediating PAD from afferents other than group I afferents. Lesions of the ipsilateral and contralateral, lateral and ventral funiculi (in addition to the dorsal columns) were made in order to define which of these funiculi are required for the appearance of the intersegmental PAD. The intersegmental PAD could evoked from the dorsal horn when either the contralateral or the ipsilateral funiculi were left intact. © 1984.
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| 4. |
- Harrison, P. J., et al.
(författare)
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Labelling of interneurones by retrograde transsynaptic transport of horseradish peroxidase from motoneurones in rats and cats
- 1984
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Ingår i: Neuroscience Letters. - : Elsevier BV. - 0304-3940. ; 45, s. 15-19
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Tidskriftsartikel (refereegranskat)abstract
- Transsynaptic transport of conjugates of wheat germ agglutinin with horseradish peroxidase (WGA-HRP) has been studied in rats and cats. WGA-HRP was injected into a muscle nerve from which it was first transported to motoneurones and along sensory fibres, and secondarily to interneurones. More extensive labelling of interneurones occurred in preparations with only relevant ventral roots intact than in preparations with only dorsal roots intact, which indicates that the transsynaptic transport of WGA-HRP is primarily in the retrograde direction, i.e. from motoneurones to interneurones. Such a transport appeared to be considerably enhanced by neuronal activity. © 1984.
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| 5. |
- Harrison, P. J., et al.
(författare)
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Shared reflex pathways of group I afferents of different cat hind‐limb muscles.
- 1983
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 338, s. 113-128
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Tidskriftsartikel (refereegranskat)abstract
- The convergence of group I muscle afferents of different muscle origin onto interneurones in spinal reflex pathways has been investigated using the technique of spatial facilitation of the transmission from afferents to motoneurones. The investigated pathways are those of non‐reciprocal inhibition and of oligosynaptic excitation of motoneurones. Extensive convergence has been found of group I afferents from muscles operating at the same and different joints onto the interneurones interposed in both excitatory and inhibitory, disynaptic and trisynaptic pathways to motoneurones. Convergence has been found between muscle spindle Ia and/or tendon organ Ib afferents from different muscles, thereby extending observations on convergence of these subgroups of group I afferents from the same muscles. The results show that group I afferents of different muscles influence motoneurones via shared neuronal pathways and that transmission from these afferents is influenced by afferents originating in other muscles. The afferent information forwarded to individual motoneurones is therefore the ensemble picture of the length and tension of many muscles. © 1983 The Physiological Society
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