Effect of diazepam on the spontaneous and harmaline-induced electrical activity of Purkinje cells in the cerebellum of the rat and rabbit

Abstract

The effect of diazepam and harmaline upon spontaneous simple spike (SS) and complex spike (CS) activity of cerebellar Purkinje cells (PC) was studied in unanaesthetized and curarized rats and rabbits. Diazepam (5 mg mg ) markedly decreased the SS activity of the Purkinje cells tested without any modification of the CS frequency. Harmaline (5–15 mg mg i.v.) induced a rhythmical activity of CS at 6–12 Hz, associated with a remaining SS activity that was also rhythmically organized in most of the Purkinje cells recorded. In rabbits the rhythmical CS discharges elicited by harmaline were suppressed by diazepam administration but only transiently (10 min). In rats diazepam did not prevent or suppress the rhythmical CS activity. These results suggest that the inhibition of harmaline-induced tremor by diazepam (Mao, Guidotti and Costa, 1975a) is not due to an inhibition of rhythmical CS activity of Purkinje cells.