The Effect of Diphenylhydantoin on Cerebellar Purkinje Cells in Rats

Abstract

Diphenylhydantoin (DPH) is one of the most widely used antiepileptic drugs, and acts to increase the spontaneous discharge of cerebellar Purkinje cells (PC). Moreover, of extrafocal inhibitory systems within the brain only the cerebellum is said to uniformly demonstrate the inhibitory effect on epileptic seizure. Therefore the effects of DPH on the PC activity were studied. Double and tetanic stimuli of the inferior olive produced depression following the initial facilitation of PC responses. Intraperitoneal administration of DPH (50 mg/kg) provoked the facilitation to a greater extent, and especially with the tetanic stimulus the responses were facilitated progressively during the stimuli, even at the frequency of 200 Hz. The chronaxie of cerebellar Purkinje axons was not significantly changed with DPH administration. These results suggest that one of the inhibitory effects of DPH on epileptic seizure is due to the increase of PC activation produced by the facilitation of the synaptic transmission in the olivocerebellar pathway.