THE RELATIVE EFFECTS OF d-AMPHETAMINE, IMIPRAMINE AND HARMALINE ON TETRABENAZINE SUPPRESSION OF SCHEDULE-CONTROLLED BEHAVIOR IN THE RAT

¹ Department of Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania

The benzoquinolizine derivatives, tetrabenazine (TBZ) and Ro 4-1284, suppress operant response rates. The effects of d-amphetamine, imipramine and harmaline in antagonizing this suppression were studied in the rat. d-Amphetamine and harmaline exerted a dose-dependent antagonism of the effects of TBZ in rats performing under either fixed-interval, variable-interval or fixed-ratio schedules of water presentation, or under a fixed-ratio schedule of electric-shock termination. Previous investigators, using relatively gross indicators of behavior, have implied that imipramine and related drugs are antagonists of the behavioral effects of TBZ and other reserpine-like drugs. On the basis of the present results, this appears unwarranted. Over a wide range of dosage and time parameters, imipramine or desmethylimipramine did not antagonize the effects of TBZ, Ro 4-1284 or reserpine on schedule-controlled behavior. Imipramine did antagonize the effects of TBZ on fixed-interval response rate in the pigeon, but, in this species, imipramine itself markedly enhances response rates.