Facilitation of tungstic acid gel-induced cortical epilepsy in rats by depression of the reticular formation.

The experiments were performed electroencephalographically (EEG) on intact and decerebrated (cerveau isolé) rats with cortical foci induced by application of tungstic acid gel. In both preparations, the gel applied cortically (15 microliter) caused generalized seizures (GS) which often recurred with a stable interictal period approximately 1 hr later. The amplitude of GS and its high frequency components induced in decerebrated animals were more pronounced than those in intact ones. The duration of GS was prolonged up to 232% as compared with that in intact ones. Administration of chlorpromazine or biperiden in intact animals enhanced GS at the doses depressing EEG arousal response induced by electrical stimulation of the sciatic nerve, but did not enhance GS in decerebrated animals. The anticonvulsive effect of phenobarbital and diazepam in decerebrated animals was stronger than that in intact ones, while the effect of diphenylhydantoin and dipropylacetate was the same in both preparations. It is suggested in the gel-induced epilepsy that either impairment or depression of the reticular formation enhances GS.