LEARNED SUPPRESSION OF STEREOTYPY IN AMPHETAMINE-TREATED RATS - IMPLICATIONS FOR UNDERSTANDING TOLERANCE TO AMPHETAMINE ANOREXIA

The purpose of this study was to determine whether amphetamine-treated rats can learn to suppress stereotyped movements in order to feed. Ra ts implanted with cannulae were reinforced with intraoral infusions of milk for holding their heads stationary within a narrow area of space defined by intersecting photobeams. Four of six rats given chronic in jections of amphetamine (2 mg/kg) learned the response. The amount of milk ingested as a result of the infusions increased over trials at a rate that was comparable to that of rats given milk in bottles. Despit e the development of such 'tolerance', analysis of the temporal distri bution of photobeam interruptions revealed residual effects of the dru g. Specifically, amphetamine-treated rats had longer latencies to init iate infusions and displayed a more fragmented pattern of responding t han did saline controls. These results demonstrate that rats can learn to inhibit amphetamine-induced stereotypy and support the view that t olerance to amphetamine 'anorexia' involves learning to suppress stere otyped movements that interfere with feeding. Parallels to the suppres sion of involuntary movements in humans are noted.