Role of brain dopaminergic mechanisms in rodent aggressive behavior: influence of (+/-)N-n-propyl-norapomorphine on three experimental models.

(+/-)N-n-Propyl-norapomorphine (NPA), a potent agonist of brain dopamine receptors, influences aggressive behavior, but the type of influence depends on the experimental conditions. In rats, NPA increases aggression elicited by electrical foot shock, but decreases predatory aggression against turtles as well as isolation-induced aggression in male mice. NPA proves more potent than apomorphine in both the foot shock and predatory test. A per se ineffective dose of haloperidol (0.05 mg/kg-1 IP) antagonizes NPA in the rat foot shock test as well as in the isolated male mouse test. The relevance of stereotyped movements for NPA influence on aggressive behavior is briefly discussed.