Stages of constant amphetamine intoxication: delayed appearance of abnormal social behaviors in rat colonies.

Rats in colonies were observed for 7 days after half of them were implanted with slow-release silicone pellets containing d-amphetamine base. The drug-implanted animals were initially hyperactive and exploratory, but this gradually evolved over the next 24 h into motor stereotypies of an increasingly more circumscribed nature. On the 4th day after amphetamine implantation they transiently withdrew to the burrows area; thereafter they were characterized by heightened startle responses and increased social behaviors such as fighting and fleeing. During the last phase some of the drug-implanted animals tended to focus their fighting behaviors on one other drug-implanted animal. This late phase of constant amphetamine intoxication in rats has a number of similarities to amphetamine psychosis in humans, and can serve as a useful animal model for the study of its biochemical correlates.