Rhythmic firing of Deiters' neurons and synchronization by cerebellar inhibition in lidocaine-treated cats.

Cerebellar inhibition of spontaneous or homocysteic acid-induced activity of dorsal Deiters' neurons was studied in cats anesthetized with chloralose-urethane. Following intravenous lidocaine (5-10 mg/kg), cerebellar inhibition was not reduced but postinhibitory peaks (PIPs) appeared in the poststimulus histograms. The number of PIPs increased as variability in firing rate decreased after lidocaine. The frequency of PIPs observed in the histograms approximated the monitored firing rates of the cells. The peaks observed in autocorrelograms constructed after lidocaine had the same frequency, structure and variability as the PIPs. In 'dot diagrams', only one spike per corresponding PIP was observed. Similar PIPs were observed in poststimulus histograms constructed during inhibition of crayfish stretch receptor neurons which fired regularly in the absence of lidocaine. These studies indicate that the postinhibitory peaks and silent periods were due to synchronized firing of Deiters' neurons induced by cerebellar inhibition, which was detectable only after lidocaine regularized the firing of Deiters' neurons.