Evidence for dopamine mediation of submissive gestures in the stumptail macaque monkey.

Dopamine systems help regulate submissive behavior in Stumptail macaques. Chronic administration of d-amphetamine (3.2 mg/kg/day for 12 days) significantly increased submissive gestures in some treated monkeys, even without a concurrent increase in aggression from others. This effect was blocked by haloperidol and pimozide, drugs that block dopamine receptors. The dopamine agonist apomorphine caused a large, dose-dependent increase in submissive gestures; repeated apomorphine (1.0 mg/kg/day for 12 days) produced a similar increase to amphetamine in monkeys previously treated with amphetamine. The hallucinogen 5-methoxy N,N-dimethyltryptamine also increased submissive gestures via dopamine systems, as dopamine blockers antagonized this response while serotonin antagonists did not. These findings may relate to drug-induced and endogenous psychopathologies in humans.

Study at a glance

Abstract

Evidence gathered from several experiments where stimulant drugs were given to selected members of adult Stumptail macaque social colonies is presented which suggests that dopamine systems play an important part in the mediation of submissive behavior in this species. Chronic administration of d-amphetamine, 3.2 mg/kg/day, for 12 days, induced a significant increase in submissive gestures displayed by some treated monkeys despite the lack of a significant concurrent increase in aggressive gestures directed toward these animals. This behavioral change was antagonized by haloperidol and pimozide, two agents with preferential dopamine receptor blocking properties. The dopamine receptor agonist apomorphine induced a large dose-dependent increase in submissive gestures displayed by treated monkeys. Repeated administration of apomorphine, 1.0 mg/kg/day, for 12 days, induced a significant increase in submissive gestures comparable to amphetamine in monkeys who had previously received chronic d-amphetamine treatment. In addition, it appears that the significant increase in submissive gestures by monkeys treated with the hallucinogen 5-methoxy N,N-dimethyltryptamine is also mediated through dopamine systems since the preferential dopamine receptor blockers haloperidol and trifluoperazine antagonized this response while the serotonin antagonists cinanserin, methysergide, metergoline, and cyproheptadine all failed to antagonize or even potentiate this behavioral change. These results have important implications in the study of animal behavior and may have relevance to drug-induced and endogenous psychopathologies in humans as well.