Effects of psychotropic drugs on hypothalamic self-stimulation behavior in rats.

* Results of this investigation were presented at the 43rd (June , 1973) Kinki Regional Meeting of Japanese Pharmacological Society. AbstractEffects of psychotropic drugs on intracranial self-stimulation behavior were investigated in rats with chronic electrodes implanted in the lateral posterior hypothalamus. Major tranquilizers such as chlorpromazine, levomepromazine, haloperidol, clozapine and oxypertine caused a selective depression of self-stimu lation at non-debilitating doses, and a dose-response relationship was also observed. Diazepam depressed this behavior at a dose much larger than that impairing rotarod performance. Chlordiazepoxide, on the contrary, failed to depress self-stimulation even at 50 mg/kg, and rather slightly facilitated this behavior at smaller doses. The mode of action of pentobarbital was similar to that of diazepam. Antidepressants, imipramine and amitriptyline depressed this behavior only at doses larger than those which significantly impaired coordinated motor activity. Methamphetamine rather facilitated self-stimulation at 0.5-1 mg/kg, but depressed it at 5 mg/kg. It is con eluded that hypothalamic self-stimulation is most selectively depressed by major tranquilizers.