| 1. |
- Jankowska, Elzbieta, et al.
(författare)
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A long propriospinal system with direct effect on motoneurones and on interneurones in the cat lumbosacral cord
- 1974
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Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 21, s. 169-194
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Tidskriftsartikel (refereegranskat)abstract
- Stimulation of the lateral funicle was performed at different segmenta levels in the cat in order to investigate the connecxions of long propriospinal neurones with ipsilateral lumbosacral motoneurones and interneurones projecting directly to them. In one series of experiments the propriospinal contribution was assessed from the difference between the effect of maximal stimulation in C 1 (activating supraspinal descending fibres) and in more caudal segments (activating supraspinal and propriospinal fibres). In another series on cats with chronic hemisection in C 3 pure propriospinal effects were evoked by stimulation of the thoracic spinal cord. In both series it was shown that volleys in long propriospinal neurones evoke monosynaptic EPSPs and disynaptic EPSP and/or IPSP in many flexor and extensor motoneurones; an extracellular monosynaptic focal synaptic potential was recorded in lamina VII of Rexed. The effects evoked by stimulation of the Th 11 segment after chronic C 3 hemisection were not found after chronic Th 10 hemisection. It is therefore tentatively suggested that they were due to stimulation of long descending propriospinal neurones originating in the lower cervical and upper thoracic segments, their axon trajectory being in the middle of the lateral funiculus and conduct at velocity 100 m/sec. Other effects evoked by stimulation of Th 11 after chronic Th 10 hemisection are ascribed to antidromic activation of axons of ascending neurones. © 1974 Springer-Verlag.
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| 2. |
- Jankowska, Elzbieta, et al.
(författare)
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An electrophysiological demonstration of the axonal projections of single spinal interneurones in the cat
- 1972
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 222, s. 597-622
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Tidskriftsartikel (refereegranskat)abstract
- 1. Single interneurones excited from group Ia afferents and located in the ventral horn of the spinal cord in the cat were activated antidromically by stimulation of their axons with one micro‐electrode while recording extracellularly close to their somas with a second micro‐electrode. The interneurones studied were those which, according to previous indirect evidence, should mediate the reciprocal Ia inhibition of motoneurones. 2. Two subgroups of these interneurones were studied: those excited from group Ia afferents in the quadriceps (Q) and posterior bicepssemitendinosus (PBSt) nerves. Most of them could be activated from a number of separate loci in the PBSt and Q motor nuclei respectively and from the ventral or lateral funiculi. 3. The location of the axonal branches and the extent of their branching in the motor nuclei were reconstructed by comparing the latencies of the responses and the thresholds (0·1–5 μA) for antidromic activation of single interneurones from different electrode positions in a number of tracks, having previously established the relation between the threshold and the distance from the stimulated fibres. For the main branches in the white matter the conduction velocity was found to be about 70 m/sec. 4. The axonal projections of the investigated interneurones were found to be fully consistent with the hypothesis that they mediate reciprocal inhibition of motoneurones. © 1972 The Physiological Society
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| 3. |
- Jankowska, Elzbieta, et al.
(författare)
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Synaptic actions of single interneurones mediating reciprocal Ia inhibition of motoneurones
- 1972
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 222, s. 623-642
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Tidskriftsartikel (refereegranskat)abstract
- 1. The investigation was aimed at defining the function of the interneurones which, according to indirect evidence, mediate the reciprocal Ia inhibition of motoneurones (Hultborn, Jankowska & Lindstrom, 1971 b) by studying their direct synaptic actions. These actions were tested by recording post‐synaptic potentials in motoneurones following spike activity of single interneurones activated by iontophoretic application of glutamate. The interneurones were found to produce unitary monosynaptic IPSPs in those motoneurones in which disynaptic IPSPs are evoked by the group Ia afferents which monosynaptically excite the interneurones. 2. Unitary IPSPs were found in more than 80% of the motoneurones impaled in the immediate vicinity of the axonal branches of the investigated Q interneurones in the PBSt motor nucleus. It is estimated that each interneurone might inhibit about every fifth PBSt motoneurone. The amplitudes of the unitary IPSPs ranged between 8 and 220 μV and were 10–200 times smaller than the maximal Ia IPSPs evoked in the same motoneurones. 3. The synaptic delay in the generation of unitary IPSPs was measured in relation to the spike potentials recorded from the terminal branches of interneurones in the immediate vicinity of the impaled motoneurones. The synaptic delays ranged between 0·28 and 0·42 msec. 4. From chloride reversal tests and an analysis of the time course of the unitary IPSPs it was concluded that the terminals of the investigated interneurones make synaptic contact predominantly on the soma and/or on the proximal parts of the dendrites of the motoneurones, their distribution being, however, not quite uniform. © 1972 The Physiological Society
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