Self-stimulation Behavior In Rats Research Articles

Effects of various psychotropic drugs on self-stimulation behavior in the rat

Effects of various psychotropic drugs on tegmental and hypothalamic self-stimulation behavior in rats with chronically implanted electrodes in the brain were studied. Effects of elecrtical stimulation in several brain structures on self-stimulation behavior and influences of drugs on the stimulation effect were also investigated. The hypothalamic self-stimulation behavior was more markedly inhibited by chlorpromazine than the tegmental self-stimulation, whereas the latter was more strongly inhibited by diazepam. The effects of pentobarbital on the self-stimulation behavior were similar to those of diazepam. Methamphetamine facilitated both the tegmental and hypothalamic self-stimulation behavior. Suppressive effect of hypothalamic stimulation on the tegmental self-stimulation behavior was inhibed by chlorpromazine, while those of amygdaloid and septal stimulation were augmented. All the effects of hypothalamic, amygdaloid and septal stimulating on the tegmental self-stimulation behavior were inhibed by diazepam and pentobarbital, while these were facilitated by methamphetamine. Suppressive effects of tegmental, amygdaloid and septal stimulation on the hypothalamic self-stimulation behavior were all facilitated by both chlorpromazine and methamphetamine. The effects of amygdaloid and septal stimulation on this behavior were inhibed by diazepam and pentobarbital, while those of tegmental stimulation were enhanced. The effects of imipramine, in all experiments, were variable in each rat and not significant.

Effects of 5-hydroxytryptophane on self-stimulation in rats.

The effect of 5-hydroxytryptophane (5-HTP) was investigated on self-stimulation behavior in rats and orrelated with that on the contents of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) in different areas of their brain. 5-HTP (28, 57 and 115 mg/kg, i.p.) caused a dose-dependent decrease (32, 57 and 66%, respectively) in self-stimulation responding, whereas other amino acids (e.g. glycine, glutamic acid) or the vehicle had negligible effects. Concomitant with the decrease in responding, there was a significant increase in 5-HT contents of the various areas of the brain in the treated rats; the NE contents showed only a slight decrease. 5-HTP continued to decrease self-stimulation responding, in spite of pretreatment with a decarboxylase inhibitor, RO4-4602 that reduced increase in 5-HT contents of peripheral organs (e.g. heart). Brain 5-HT appears to have an inhibitory role in this behavior.

Effects of Psychotropic Drugs on Hypothalamic Self-Stimulation Behavior in Rats

Effects 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-stimulation 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 coneluded that hypothalamic self-stimulation is most selectively depressed by major tranquilizers.

Alterations by centrally acting drugs of the suppression of self-stimulation behavior in the rat by tetrabenazine, physostigmine, chlorpromazine and pentobarbital.

The effects of pre-treatment (32 min) with d-amphetamine (2 mg/kg), scopolamine (0.5 mg/kg), and chlordiazepoxide (5 mg/kg) were studied on the suppression of self-stimulation behavior in the male albino rat by central depressants. The antagonism of each compound was determined against the suppressant action of tetrabenazine (2 mg/kg), physostigmine (0.1 mg/kg), chlorpromazine (2.5 mg/kg) and pentobarbital sodium (10 mg/kg). Against the suppression produced by tetrabenazine, only d-amphetamine gave partial protection throughout the test. Scopolamine and chlordiazepoxide had a transient delaying action. Against the suppressant effect of chlorpromazine, protection was given by d-amphetamine, scopolamine and chlordiazepoxide. Against physostigmine, scopolamine gave full protection, d-amphetamine partial protection, and chlordiazepoxide was without effect. Against the effect of pentobarbital on self-stimulation behavior, there was no protection by d-amphetamine and scopolamine when the animal showed motor deficits, and a stimulant action when these had worn off, but the rates of responding were still depressed. Chlordiazepoxide potentiated the action of pentobarbital. These results are interpreted in terms of a short-run stimulant action on depressed rates of responding, and a longer-run protective action against changes produced by the compounds suppressing self-stimulation behavior in levels of transmitter-like substances.