[Vestibulospinal synaptic influences on the lumbar motor neurons of rats]

Abstract

In acute experiments on rats, studies have been made by intracellular recording of synaptic effects in lumbar motoneurons during stimulation of the ipsilateral Deiters nucleus. The nucleus was identified by recording antidromic responses of the vestibulo-spinal neurons during stimulation of the ventral surface of the II-IV lumbar segments. It was found that vestibulo-spinal fibers with different conduction velocity (from 18 up to 69 m/sec.) reach lumbar parts of the spinal cord via the ventral columns. Excitatory and inhibitory responses in the mononeurons were elicited more readily by stimulation of the Deiters nucleus by two and more stimuli. In 152 motoneurons out of 241, excitatory synaptic reactions were recorded. In all functional groups of motoneurons of muscles of the hindlimbs, predominantly polysynaptic EPSP were registered. Disynaptic EPSP were observed occasionally and only in motoneurons of the extensors. Monosynaptic vestibulo-motoneuronal EPSP was recorded in one of the 46 G-S motoneurons.