Thalamic generalized seizure induced by tungstic acid gel in cats and its suppression by anticonvulsants

The experiments were performed electroencephalographically on gallamine-immobilized cats with the thalamic foci induced by application of tungstic acid gel (gel). The gel (50 microliters) applied to n. centralis lateralis (CL) caused generalized seizure (GS) with high frequency components triggered by slow wave, and GS recurred with a regular interictal period. The application to n. centralis medialis or n. medialis dorsalis did not induce recurring GS, indicating the heterogeneity in the epileptogenesis of the thalamus. The GS induced by the gel application to the CL was of thalamic origin. Anticonvulsants used were found to prolong the interictal period of the GS, without modifying its duration. There was a difference between the drugs effective against grand mal and petit mal epilepsies in that the prolongation by the former drugs, diphenylhydantoin and phenobarbital, was more pronounced at low doses than that by the latter drugs, trimethadione and dipropylacetate. These results suggest that the gel-induced epileptic model with thalamic foci is useful for analyzing the pathophysiological process of epilepsy and for evaluating the drugs effective against grand mal epilepsy.