Effects of d,1-propranolol and haloperidol on aggressive behavior induced in mice by isolation and isolation plus amphetamine treatment.

We measured the aggressive behavior of isolated mice treated or not with d,1-amphetamine (6.0 mg/kg, ip) and injected with different doses of d,1-propranolol (10.0, 20.0 or 30.0 mg/kg, ip) or haloperidol (0.5 or 1.0 mg/kg). d,1-Amphetamine (6.0 mg/kg, ip) decreased the aggressiveness of the isolated mice and induced stereotyped behavior. Haloperidol antagonized amphetamine-induced stereotypy, increased the latency to the 1st attack and decreased duration of fighting and frequency of attacks in mice treated or not with amphetamine. d,1-Propranolol did not change stereotypy but decreased aggressiveness in a dose-dependent way, being more effective against aggression induced by isolation per se. These results are discussed in terms of the interference of the drugs with the activity of either catecholaminergic neurons or midbrain reticular formation. The latter effect seems to be the most likely explanation for the observed anti-aggressive effects of haloperidol and d-1, propranolol.