Apomorphine-induced aggression in the rat

Abstract

Summary Spontaneous aggression in male rats was observed following injections of apomorphine, 10–30 mg/kg subcutaneously. The aggressive response could be elicited following smaller doses of apomorphine, 5–10 mg/kg, by pinching the tail 30 min after apomorphine treatment. The occurrence of spontaneous fighting and pain-induced fighting following apomorphine depended upon the age of the animals. Aggression was not observed until animals had attained the age of 49–56 days. Pretreatment with reserpine lowered the threshold for induction of aggressive responses by apomorphine. With reserpine pretreatment, spontaneous aggression was observed following apomorphine in doses of 0.5–2.5 mg/kg subcutaneously. If one assumes that apomorphine is a specific agonist at dopaminergic receptors, then these results suggest that the apomorphine-induced aggressive behaviour as well as the similar mock-fighting behaviour following l -DOPA or dexamphetamine, as reported by other authors, is probably a consequence of enhanced activity at dopaminergic receptors.