Dose-dependent behavioural changes induced by apomorphine in selected members of a primate social colony

The effect of six acute doses of the dopamine receptor agonist apomorphine on non-human primate social and individual behaviour was studied in a social colony of four adult Stumptail macaques. Apomorphine was administered intramuscularly to 2 monkeys/day in doses ranging from 0.05 to 3.00 mg kg-1 15 min bfefore a 1 h observation period. Apomorphine induced hyperactivity, hypervigilance, and stereotyped behaviour at doses of 0.50 mg kg-1 and greater in all 4 monkeys. In addition it also caused a dose-dependent disruption of normal behavioural patterns. Social grooming was eliminated while the submissive gestures were significantly increased. It also induced an increase in vocalizations and suppression of food forage behaviours. The results demonstrate the role of dopamine systems in the mediation of affiliative behaviour as well as motor behaviour in a primate species. Also, since similar behavioural changes are induced in this species during chronic (+)-amphetamine treatment, it is suggested that dopamine systems play a predominant role in amphetamine-induced behaviour in primates.