FURTHER-STUDIES TO EXAMINE THE NATURE OF DEXFENFLURAMINE-INDUCED SUPPRESSION OF HEROIN SELF-ADMINISTRATION

The present series of experiments sought to investigate further the me chanism by which dexfenfluramine, a selective 5-HT releaser/reuptake i nhibitor, reduces heroin self-administration by male Wistar rats. In e xperiment 1, the effect of combined intravenous heroin and intraperito neal dexfenfluramine injections on operant responding for food was exa mined, In experiment 2, the maintenance of dexfenfluramine suppression of heroin self-administration following chronic (7 day) treatment was evaluated. Finally, in experiment 3, the ability of various 5-HT anta gonists to block the dexfenfluramine suppression was examined. The res ults from experiment 1 suggest that sensorimotor deficits/malaise pote ntially associated with heroin/dexfenfluramine combinations are unlike ly to account for the reductions in heroin self-administration. Experi ment 2 suggested that the suppressant effect of dexfenfluramine on her oin responding may diminish rapidly following chronic treatment. Final ly, central 5-HT1 and/or 5-HT2, but not 5-HT3, receptors may underlie the suppressant effects of dexfenfluramine on heroin self-administrati on.