Effect of anticonvulsants on cortical focal seizure in cats.

Electrical stimulation of the visual cortex evoked the cortical focal seizure restricted in the neighbor cortex of the stimulated area in gallamine-immobilized cats. The present experiment was performed to clarify the participation of anticonvulsants in the cortex itself. Phenytoin and carbamazepine depressed the focal seizure, as indicated by the shortening of seizure duration and the suppression of spreading. In addition, the high-frequency components in seizure disappeared with the use of these drugs. Phenobarbital and diazepam also shortened the seizure duration. However, the high-frequency components did not disappear although seizure amplitude was depressed. Trimethadione, acetazolamide, and dipropylacetate facilitated the focal seizure. From these results, the participation of the drugs affecting grand mal and partial epilepsies in the cortex is suggested. In addition, this experimental model is though to be useful in elucidating possible modes or mechanisms of anticonvulsant action on cortical neurons by analyzing, after drug administration, the changes in seizure patterns which seem to reflect underlying neuronal changes.