Differential blockade of bicuculline convulsions by neuroleptics

Haloperidol, pimozide, sulpiride and metoclopramide blocked bicuculline-induced convulsions in mice. Chlorpromazine and thioridazine exhibited this effect at low doses whereas at higher doses (e.g. 1 mg/kg i.p. chlorpromazine) this activity was no longer apparent. A dose of phenoxybenzamine which was inactive alone (7.5 mg/kg i.p.) completely blocked the anti-bicuculline effect of sulpiride and antagonized that of haloperidol. These data are interpreted as indicating that intact noradrenergic systems are necessary for the anti-bicuculline effect of the neuroleptics.