Fig. 6.

Discriminative stimulus effects of a combination of midazolam and pregnanolone after administration of vehicle (○) or various doses of flumazenil in four monkeys (subjects HE, SA, LI, and NI). Abscissa, dose in milligrams per kilogram body weight with the top label on the abscissa indicating the dose of midazolam and the bottom label indicating the dose of pregnanolone; data above V represent the effects of vehicle. Doses of midazolam and pregnanolone were multiples of ED₅₀ values obtained when that drug was studied alone; those values were 0.051 mg/kg for midazolam and 3.45 mg/kg for pregnanolone. Ordinate, mean (±1 S.E.M.) percentage of total responding that occurred on the midazolam lever.