Inhibition of Vestibular Nerve Activity by Efferent Fibres in the Cat

Abstract

Electrophysiological studies were performed in anesthetized cats to examine the role of the parvocellular reticular nucleus (PCRN) in vestibular afferent fibers originating in the horizontal semicircular canal. When the primary afferent fibres intra-axonally recorded in the brainstem were classified into regular, intermediate, and irregular types, repetitive stimuli over 100 Hz applied to the PCRN inhibited spontaneous firing and the increase in firing during horizontal rotation in irregular and intermediate type units, whereas in regular type units PCRN stimulation affected neither the spontaneous firing nor rotation-induced responses. These results strongly suggest that the PCRN stimulation inhibits the primary afferent terminals of irregular type units receiving impulses from type I hair cells of the ampullae.

Key Words:

• vestibular efferent fibres
• horizontal rotation
• intra-axonal recording