Evidence that supersensitivity after recovery from 6-hydroxydopamine is an artifact of isolation housing

Rats were administered intraventricular injections of 6-hydroxydopamine (6-OHDA) and allowed to recover in either isolation cages or in an enriched, non-crowded rat colony environment. When tested 45 days after 6-OHDA, the animals allowed to recover in isolation cages were hyperirritable, reared more in open field than did isolated controls, and showed exaggerated responsivity to d-amphetamine. None of these effects, which have been ascribed to the development of supersensitivity, were present in the rats allowed to recover in the colony environment. This implies that the process of recovery from 6-OHDA is different in isolated and enriched social environments.