The evaluation of different types of anti-convulsant drug activity against leptazol-induced epileptogenic activity in the anaesthetized rat.

1 The effects of various anticonvulsant drugs were evaluated quantitatively on the development of the epileptogenic EEG, induced by the intravenous infusion of leptazol in rats anaesthetized with urethane. 2 Leptazol alone produced five distinct phases of EEG activity developing from early wave and small spike and wave activity to larger spikes which later grouped and led to full body convulsion (FBC). 3 Drugs effective in petit mal such as clonazepam (0.1 and 0.25 mg kg-1) and ethosuximide (100 and 200 mg kg-1), significantly delayed the time to FBC by prolonging the early phases of the epileptogenic EEG and delaying the appearance of spiking. 4 Drugs effective in grand mal such as sodium valproate (60 mg kg-1) and phenytoin (5 mg kg-1) significantly prolonged the time to FBC by extending the later phases of the EEG and the development and grouping of spikes. Higher doses of these compounds were without effect. Carbamazepine and phenobarbitone produced mixed effects but were generally not markedly anticonvulsant. 5 The model is sensitive to drugs effective in both petit mal and grand mal, and appears able to differentiate usefully between them.