Electrophysiologic and anatomic demonstration of inhibitory commisural vestibular neurons in the tench (Tinca tinca)]

Horseradish peroxydase was injected intracellularly in some of the medullary neurons which, in Fish, exhibit a passive hyperpolarizing potential after spinal cord stimulation (this indicates that such neurons both electrical and chemical inhibitions of the Mauthner cells). With positive staining, commissural vestibular neurons were identified; their axons cross the midline and they establish connexions with the Mauthner cell and with vestibular neurons of both sides. Thus the existence of a crossed vestibular inhibitory pathway, previously suggested by electrophysiological studies in lower Vertebrates as well as in Mammals, is now correlated with histological evidence.