The schedule dependent effects of 3-quinuclidinyl benzilate on operant behavior in the rat

The effects of 3-quinuclidinyl benzilate (QNB) on performance maintained by a fixed-ratio 20 (FR-20) or a differential-reinforcement-of-low-rate 20 sec. (DRL-20) schedule for water reinforcement were studied in rats. Graded doses of QNB (range 0.0125-0.2 mg/kg) were administered IP immediately prior to 30 min test sessions. QNB had a biphasic effect on FR responding: at a low dose (0.0125 mg/kg) it increased, while at higher doses (0.05-0.2 mg/kg) it decreased mean response rate in a linear, dose-dependent, manner. QNB had only a monotonic effect on DRL responding; doses of 0.05-0.2 mg/kg increased the mean response rate and decreased reinforcement rate in a dose-related fashion. The ED50's for loss of reinforcement were identical (0.07 mg/kg) for both schedules. The findings indicate that QNB may exert rate dependent effects.