| 221. |
- Jankowska, Elzbieta, et al.
(författare)
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Morphology of interneurones mediating Ia reciprocal inhibition of motoneurones in the spinal cord of the cat
- 1972
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 226, s. 805-823
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Tidskriftsartikel (refereegranskat)abstract
- 1. Interneurones identified by physiological criteria (Hultborn, Jankowska & Lindström, 1971b) to mediate Ia reciprocal inhibition of motoneurones in the spinal cord of the cat were stained by intracellular injection of a fluorescent dye (Procion Yellow). 2. The somas of the stained cells were found in Rexed's lamina VII, just dorsal or dorsomedial to the motor nuclei. Their size was about 30 × 20 μm. The cells had four to five slender, weakly branching dendrites. The total extension of their dendritic trees was about 600 μm dorsoventrally, 400 μm mediolaterally and 300 μm rostrocaudally. 3. The axons originated from a separate axon hillock or from the base of a dendrite. They were myelinated with external diameter of about 6–14 μm and projected to either the ipsilateral ventral or lateral funiculi. Early collaterals were found only exceptionally. Some axons bifurcated into an ascending and a descending branch within the funiculi. 4. The possibility of identifying the Ia inhibitory interneurones on purely morphological grounds is discussed. © 1972 The Physiological Society
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| 225. |
- Jankowska, Elzbieta, et al.
(författare)
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Projections of pyramidal tract cells to alpha‐motoneurones innervating hind‐limb muscles in the monkey.
- 1975
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 249, s. 637-667
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Tidskriftsartikel (refereegranskat)abstract
- 1. We have investigated the spatial organization of monosynaptic corticospinal projections to hind‐limb motoneurones, using near threshold stimulation of the surface of the precentral gyrus to activate pyramidal tract (PT) cells and intracellular recording from motoneurones to detect the resulting e.p.s.p.s. 2. Monosynaptic e.p.s.p.s. of cortical origin were seen in all motoneurone species investigated, those of distal as well as of proximal hind‐limb muscles. The proportion of motoneurones in which the e.s.p.s. were evoked and the amplitudes of the latter indicated a more extensive cortical projection to motor nuclei for distal than for proximal muscles, as previously found for forelimb motoneurones. 3. Cortical areas from which monosynaptic e.p.s.p.s. were evoked in individual motoneurones were remarkably large, most often between 3 and 7 mm2. Several motoneurones appeared to have two or three separate areas within the hind‐limb division of the motor cortex. 4. Areas of location of pyramidal tract cells projecting to various motoneurones innervating one muscle were usually not identical. They overlapped often only partially or did not overlap at all. 5. Areas of location of pyramidal tract cells projecting to motor nuclei for different muscles often showed an extensive overlap. When it occurred, various motoneurones of a given motor nucleus had common cortical projection areas with motoneurones of other motor nuclei, either to synergistic or to antagonistic muscles. Our results give further evidence for overlapping of areas of cortical projections to motoneurones and speak against a mosaic‐like organization of pyramidal tract cells projecting to different motor nuclei. 6. The rise times of cortically evoked e.p.s.p.s. indicate that the corticospinal tract fibres terminate on motoneurones at approximately similar distances from the soma as group Ia afferents. The small amplitudes of the majority of e.p.s.p.s. evoked by near threshold cortical stimulation therefore suggest that unitary e.p.s.p.s of cortical origin are small and that the density of pyramidal tract cells projecting to individual motoneurones is usually low, even in the centrum of projection areas. 7. Effects of intracortical stimulation depended on the stimulus strength. With currents of 2‐3 muA, e.p.s.p.s were usually evoked in one motoneurone species or in close synergists. With currents of 5‐10 muA, largest e.p.s.p.s a number of other motoneurones. Latencies of descending volleys in the lumbar corticospinal tract indicated that intracortical stimuli activated pyramidal tract cells indirectly; the effects of these stimuli could thus not be used to indicate the location of pyramidal tract cells responsible for them. © 1975 The Physiological Society
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| 227. |
- Jankowska, Elzbieta, et al.
(författare)
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Segmental and supraspinal input to cells of origin of non‐primary fibres in the feline dorsal columns.
- 1979
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 290, s. 185-200
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Tidskriftsartikel (refereegranskat)abstract
- 1. The synaptic input to ascending tract cells with axons in the dorsal columns was investigated using intracellular recording. 2. E.p.s.p.s evoked by stimulation of the lateral funiculus were analysed to test for the possibility of collateral connexions between spino‐cervical tract cells and dorsal column cells. Three groups of fibres were found to contribute to such e.p.s.p.s: fibres which terminated or originated between spinal segments C3‐4 and C1, or Th9 and C3‐4 and cortico‐spinal tract fibres. The latencies and thresholds of e.p.s.p.s evoked by stimulation of the first group of fibres were compatible with their origin via axon collaterals of spino‐cervical tract cells. The occurrence of these e.p.s.p.s in dorsal column cells which were disynaptically excited from cutaneous afferents further corroborated this possibility. 3. E.P.S.P.S of specifically cervical origin were also found in some other neurones in the dorsal horn, probably segmental interneurones, but were absent in spinocervical tract cells. 4. Convergence of group I muscle afferents (possibly both group Ia and group Ib) and cutaneous afferents was found in about 50% of the dorsal column cells. The shortest latency e.p.s.p.s from cutaneous and group I afferents were evoked with segmental delays indicating monosynaptic and disynaptic coupling. 5. I.p.s.p.s were evoked from cutaneous and group I muscle afferents in either the same or different nerves as those from which the e.p.s.p.s were elicited. Excitatory potentials were, however, dominating. © 1979 The Physiological Society
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| 229. |
- 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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