AMPHETAMINE ANALOGS HAVE DIFFERENTIAL-EFFECTS ON DRL 36-S SCHEDULE PERFORMANCE

Amphetamine and related compounds have previously been shown to differ entially release dopamine (DA) and serotonin (5HT) in vivo and in vitr o. The purpose of this report is directly to compare five amphetamine analogs on differential reinforcement of low rate 36-s (DRL 36-s) sche dule performance, and to determine whether the reported increases in d opamine and/or serotonin release induced by these drugs can be related to observed behavioral differences. Amphetamine (AMPH) and methamphet amine (METH) induced large increases in response rate, methylenedioxym ethamphetamine (MDMA) and para-chloroamphetamine (PCA) caused small in creases in response rate, while fenfluramine (FEN) had no effect on re sponse rate. AMPH, METH, PCA and MDMA caused a dose-dependent decrease in reinforcement rate, and FEN had no effect on reinforcement rate. A MPH, METH, and PCA but not FEN, shifted the peak of the inter-response time (IRT) distribution toward shorter intervals, MDMA decreased peak location only at the highest dose. All five drugs caused a dose-depen dent decrease in peak area, indicating a loss of schedule control on t he DRL 36-s schedule. Consistent with in vitro and in vivo release stu dies, the differential results of these five drugs on DRL 36-s schedul e performance suggest a predominant dopamine role for AMPH and METH, a predominant serotonin role for FEN, and different degrees of combined dopaminergic and serotonergic roles for MDMA and PCA in the mediation of the task.