Facilitation of bicuculline- and picrotoxin-induced seizures by sodium valproate in rats.

Paralysed rats anaesthetized with urethane or halothane were injected with bicuculline or picrotoxin at doses which induced seizure activity in the EEG. Sodium valproate (50--1200 mg/kg) or saline was injected i.p. and its effect on the amplitude and duration of the seizures was measured. The seizures induced by either convulsant were increased significantly by doses of valproate greater than or equal to 200 mg/kg. The sites of action of the drugs in the brain, and the possible transmitter mechanisms involved, are discussed.