Transmission in the pathway of reciprocal Ia inhibition to motoneurones and its control during the tonic stretch reflex.

Publisher Summary The wide excitatory and inhibitory convergence on the interneurones mediating the disynaptic Ia reciprocal inhibition first emerged from the studies on facilitation and inhibition of test Ia inhibitory postsynaptic potentials (IPSPs) recorded in motoneurones. They revealed that several descending, as well as segmental pathways, excited the interneurones mediating reciprocal Ia inhibition. It was also found that antidromic stimulation of ventral roots could depress transmission in the Ia inhibitory pathway by an inhibition of the interposed interneurone. This chapter discusses the functional significance of the excitatory convergence from Ia afferents and descending segmental pathways on the interneurones mediating reciprocal Ia inhibition (α–γ linkage in the reciprocal inhibition) in relation to the total α–γ linked servo-control of movements. The recurrent inhibition of the interneurones mediating the α–γ linked reciprocal inhibition may serve as a segmental autoregulatory mechanism that prevents the reciprocal inhibition from getting too deep during increased α–γ linked excitation of agonists. It emerges that the interneurones in the reciprocal Ia inhibitory pathway serve as efficient integrative centers.

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