Gabamimetic properties of anxiolytic drugs.

Diazepam (5 mg/kg, ip) and tracazolate (40 mg/kg, ip), a nonbenzodiazepine anxiolytic, blocked electrically-induced head-turning without producing sedation. Bicuculline and picrotoxin, GABA antagonists, at doses not affecting head-turning (2 mg/kg, ip) antagonized the effects of diazepam and tracazolate on head-turning. However, at the same dose, bicuculline was more effective as an antagonist of diazepam whereas picrotoxin was more effective as an antagonist of tracazolate. These results suggest that benzodiazepine as well as nonbenzodiazepine anxiolytics possess GABAmimetic activity. The difference in potency between bicuculline and picrotoxin as antagonists of diazepam and tracazolate may be related to their reported differences as GABA antagonists (e.g., site of receptor interaction).