Possible interneurons responsible for reflex inhibition of motoneurons of jaw-closing muscles from the inferior dental nerve.

Abstract

In cats anesthetized with pentobarbital, the location and electrophysiological characteristics of possible inhibitory interneurons for the IPSP [inhibitory postsynaptic potential] in motoneurons of jaw-closing muscles from the inferior dental nerve were studied. The presumed inhibitory interneurons were activated monosynaptically from the low threshold afferents, and fired repetitively with intervals of about one msec. When these characteristics were observed, the dye was injected electrophoretic-ally. The region where such units were found was dorso-medial to the Vth motor nucleus, roughly corresponding to the supratrigeminal nucleus of Lorente de No. When this region was stimulated with a concentric bipolar electrode, monosynaptic IPSP was recorded in motoneurons of jaw-closing muscles of either side. Further, a shock to the contralateral inferior dental nerve evoked disynaptic IPSP on the motoneurons of jaw-closing muscles.