[Electrophysiological responses of cerebellum after the administration of diphenylhydantoin (author's transl)].

Experiments were performed to see the mechanism of anticonvulsive action of Diphenylhydantoin (DPH) especially in relation to the cerebellum. 15 normal adult cats were divided into three groups. After the intravenous administration of 10 mg, 20 mg and 30 mg/kg of DPH in each group, electrophysiological responses of the cerebellum with regard to Purkinje cell action potentials and the cerebellar electrocorticogram were observed for two hours. Purkinje cell action potentials were evaluated in its discharge rates, which were calculated with medical computer. The cerebellar electrocorticogram were analyzed with Fast Fourier Transform method especially in its Adrian rhythm (150--250). It has been demonstrated that Purkinje cell discharge rates increased extremely after a transient suppressed phase, but fast waves of the cerebellar electrocorticogram showed no remarkable changes following the administration of DPH. Plasma DPH concentration went up to a toxic level immediately after DPH injection, but returned to the plateau level after ten to thirty minutes which gradually decreased for two hours. Distribution of DPH was always higher in the cerebellum than in the cerebrum. Recent experimental and clinical studies are suggesting that the cerebellum acts as one of the important intrinsic inhibitory system against epilepsy. Our results seem to imply that DPH exerts its anticonvulsive effect by potentiating inhibitory mechanism of Purkinje cells over the cerebral cortex. The cerebellar electrocorticogram and the Purkinje cell unit activities showed no definite correlative responses to DPH administration. This will suggest that cerebellar electrocorticogram is not the only reflection of the Purkinje cell activity but the total electrophysiological phenomena of the cerebellar cortex.