Convergence on interneurones mediating the reciprocal Ia inhibition of motoneurones. III. Effects from supraspinal pathways.

Supraspinal effects were investigated in interneurones identified as mediating the disynaptic reciprocal Ia inhibition of motoneurones (referred to as Ia inhibitory interneurones). It was revealed that volleys in the vestibulospinal tract may evoke mono- and disynaptic EPSPs in interneurones monosynaptically excited from extensor muscles, i.e. extensor coupled Ia inhibitory interneurones. Flexor coupled interneurones instead received disynaptic inhibition. Volleys in the rubrospinal tract evoked a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled interneurones. Disynaptic rubrospinal EPSPs and IPSPs were also revealed. The pyramidal tract also gives rise to a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled Ia inhibitory interneurones. Rubrospinal and pyramidal volleys were shown to facilitate transmission in various segmental reflex pathways to the Ia inhibitory interneurones. A detailed comparison reveals a striking parallelism of segmental and supraspinal effects on alpha-motoneurones and Ia inhibitory interneurones connected to the same muscles. This considerably strengthens the hypothesis of an "alpha-gamma-linkage in the reciprocal inhibition".

[1]  P. Voorhoeve,et al.  Effects from the pyramidal tract on spinal reflex arcs. , 1962, Acta physiologica Scandinavica.

[2]  R. Nyberg‐hansen,et al.  Sites and mode of termination of fibers of the vestibulospinal tract in the cat. An experimental study with silver impregnation methods , 1964, The Journal of comparative neurology.

[3]  S Grillner,et al.  The origin of a descending pathway with monosynaptic action on flexor motoneurones. , 1968, Acta physiologica Scandinavica.

[4]  N. Tsukahara,et al.  Collateral pyramidal influences on the corticorubrospinal system. , 1968, Journal of neurophysiology.

[5]  S. Grillner,et al.  Reciprocal effects between two descending bulbospinal systems with monosynaptic connections to spinal motoneurones. , 1968, Brain research.

[6]  S Grillner,et al.  Supraspinal and segmental control of static and dynamic gamma-motoneurones in the cat. , 1969, Acta physiologica Scandinavica. Supplementum.

[7]  A. I. Shapovalov,et al.  Synaptic actions evoked from the red nucleus on the spinal alpha-motorneurons in the Rhesus monkey. , 1971, Brain research.

[8]  T. Hongo,et al.  Effects from the vestibulospinal tract on the contralateral hindlimb motoneurones in the cat. , 1971, Brain research.

[9]  E Jankowska,et al.  Recurrent inhibition from motor axon collaterals of transmission in the Ia inhibitory pathway to motoneurones , 1971, The Journal of physiology.

[10]  H. Hultborn,et al.  Recurrent inhibition of interneurones monosynaptically activated from group Ia afferents , 1971, The Journal of physiology.

[11]  H. Hultborn,et al.  Relative contribution from different nerves to recurrent depression of Ia IPSPs in motoneurones , 1971, The Journal of physiology.

[12]  R. Tanaka,et al.  Reciprocal group I inhibition on triceps surae motoneurons in man. , 1971, Journal of neurophysiology.

[13]  A. Lundberg,et al.  Rubrospinal monosynaptic connexion with last-order interneurones of polysynaptic reflex paths. , 1971, Brain research.

[14]  E Jankowska,et al.  Synaptic actions of single interneurones mediating reciprocal Ia inhibition of motoneurones , 1972, The Journal of physiology.

[15]  H. Hultborn,et al.  Supraspinal control of monosynaptically activated group Ia interneurones in the ventral horn. , 1972, Acta physiologica Scandinavica.

[16]  H Hultborn,et al.  Convergence on interneurones in the reciprocal Ia inhibitory pathway to motoneurones. , 1972, Acta physiologica Scandinavica. Supplementum.

[17]  H. Hultborn,et al.  Convergence in the reciprocal Ia inhibitory pathway of excitation from descending pathways and inhibition from motor axon collaterals. , 1972, Acta physiologica Scandinavica.

[18]  E. Jankowska,et al.  An electrophysiological demonstration of the axonal projections of single spinal interneurones in the cat , 1972, The Journal of physiology.

[19]  H. Hultborn,et al.  Recurrent depression from motor axon collaterals of supraspinal inhibition in motoneurones. , 1972, Acta physiologica Scandinavica.

[20]  H. Hultborn,et al.  Facilitation from ipsilateral primary afferents of interneuronal transmission in the Ia inhibitory pathway to motoneurones. , 1972, Acta physiologica Scandinavica.

[21]  D. Stuart,et al.  Propriospinal control of last order interneurones of spinal reflex pathways in the cat. , 1973, Brain research.

[22]  ALPHA-GAMMA-Linkage in the spinal generator for locomotion in the cat. , 1975, Acta physiologica Scandinavica.

[23]  G. Orlovsky,et al.  Activity of interneurons mediating reciprocal 1a inhibition during locomotion , 1975, Brain Research.

[24]  M Illert,et al.  Convergence on interneurones mediating the reciprocal Ia inhibition of motoneurones. I. Disynaptic Ia inhibition of Ia inhibitory interneurones. , 1976, Acta physiologica Scandinavica.

[25]  H. Hultborn,et al.  Convergence on interneurones mediating the reciprocal Ia inhibition of motoneurones. II. Effects from segmental flexor reflex pathways. , 1976, Acta physiologica Scandinavica.