Potentiation by intraventricular muscimol of the anticonflict effect of benzodiazepines.

The anticonflict action of muscimol (a potent GABA receptor agonist) and its ability to potentiate the anticonflict action of the benzodiazepines was studied in rats using VOgel's procedure. Rats were injected intraventricularly with a dose of muscimol from 50 to 200 ng to study whether the anticonflict action was dose-related. The potency of a 200 ng dose of muscimol is comparable to the potency of an anticonflict dose of 0.5 mg i.v. of diazepam. THIP (a muscimol analogue with weaker intrinsic GABA-mimetic activity) is active in doses 10 times higher than muscimol. The threshold dose of diazepam (0.2 mg/kg i.v.) to elicit anticonflict action was markedly potentiated when it was injected 5 min after intraventricular muscimol (150 ng). These data support the concept that GABA receptors may be involved in the anticonflict effects of the benzodiazepines.