Task-specific tolerance to d-amphetamine.

Rats were trained concurrently on sweetened-milk drinking and bar-press-responding behavior, which alternated on a daily basis. Dose-response functions for d-amphetamine were determined before and after conditions of chronic treatment. When given before chronic treatment, d-amphetamine decreased both milk consumption and reinforcement received for lever-pressing in a dose-dependent manner. Subsequently, three conditions of chronic injection were established in which one group received saline, prior to both tasks, another group received d-amphetamine prior to drinking milk and saline prior to lever-pressing and the third group received d-amphetamine prior to lever-pressing and saline before drinking milk. The rats became tolerant to d-amphetamine in the task in which the drug had been administered chronically; however, the same rats showed no tolerance in the other task in which saline had been administered chronically. Tolerance to d-amphetamine was thus shown to be behaviorally specific.