EFFECTS OF CHLORDIAZEPOXIDE, BUSPIRONE AND COCAINE ON BEHAVIOR SUPPRESSED BY TIMEOUT PRESENTATION

Male Wistar rats were exposed to a two-component multiple schedule: a random-interval 30 s schedule of pellet presentation and a conjoint ra ndom-interval 30 s schedule of pellet presentation, random-interval 2 s schedule of timeout 10 s presentation. Once responding had stabilize d subjects were injected intraperitoneally with vehicle, chlordiazepox ide (1-30 mg/kg), buspirone (0.1-4.2 mg/kg) or cocaine (1-30 mg/kg), 1 5 min before the start of the experimental session. Before drug admini stration, punished response rates were less than 30% of unpunished res ponse rates for four of the six subjects, and 60% and 75% for the othe r two. Low doses of chlordiazepoxide (1 and 3 mg/kg) increased punishe d responding (range 25-300%), and slightly increased unpunished respon se rates (by 25% in all but one subject, whose rates increased hy 75%) . The higher doses of chlordiazepoxide (10-30 mg/kg) dose-dependently decreased response rates in both components. The lower doses of buspir one (0.1 and 0.3 mg/kg) either did not affect, or decreased response r ates in both components of the schedule; the higher doses produced dos e-dependent decreases. Low doses of cocaine (1, 3 and 5.6 mg/kg) did n ot affect response rates in either component of the multiple schedule, whereas higher doses produced a dose-dependent decrease in response r ates, except for one subject whose punished response rates increased s ubstantially. The behavioral effects of chlordiazepoxide and buspirone observed in the present experiment were similar to those observed in experiments in which response rates were suppressed by shock presentat ion.