DIFFERENTIAL EFFECTS OF ANTIEPILEPTICS ON HIPPOCAMPAL AND PALLIDAL AFTERDISCHARGES IN CATS

Abstract

Many investigators reported that the hippocampus (HPC) was involved in cerebral and cerebellar seizure discharges and epileptiform phenomena (1-4), and it was the well known site of histological lesion which was found in approximately 50 per cent of epileptic brains (5, 6). The HPC has the lowest threshold of excitability to electrical stimulus of all the cerebral structues so far studied since reported by Kaada (1). Pathologically and electrophysiologically the sensitive structure of brain is suggested to play an essential part in the development of the epileptic seizures.
Several ablation and electrophysiological experiments on the brains (7-13) have confirmed that extrapyradmidal structures play a predominant part in the mechanism of generalized convulsion, and that convulsion has not cortical origin followed with corticospinal propagation. For the relief of tremor and rigidity in extrapyramidal diseases, the surgical lesion is often made in the globus pallidus (GP) (14). Most characteristic response to electrical stimulation of GP is tremor in human (15).
The present investigation was undertaken to evaluate the effects of clinically known antiepileptics quantitatively on the both hippocampal and pallidal seizures with special reference to threshold voltage and afterdischarge propagation induced by electrical stimulation of both HPC and GP.