Increased successive negative contrast in rats withdrawn from an escalating-dose schedule of D-amphetamine.

The exposure of humans and animals to high doses of psychostimulant drugs, followed by their withdrawal, leads to a number of aversive psychological symptoms. These symptoms include increased anxiety and anhedonia, and may be manifested behaviorally as a decreased interest in normally rewarding stimuli. In the present study, we determine the effects of withdrawal from an escalating-dose schedule of D-amphetamine on the consumption of a 4% sucrose solution under normal conditions, and after an incentive downshift. The downshift was induced by subjecting animals to a consumatory negative contrast paradigm, by switching them from a familiar 32% sucrose solution to a novel 4% solution. In unshifted animals, there was no effect of D-amphetamine withdrawal on consumption of the 4% solution. In contrast, drug-withdrawn animals displayed an exaggerated negative contrast effect, primarily reflected as a delayed recovery from the downshift lasting for at least 60 h. This effect is interpreted as a consequence of the increased emotionality of withdrawn animals, and may be related to disruption of normal search behaviors.