Effects of repeated withdrawal from continuous amphetamine administration on brain reward function in rats

Rationale: The study of the effects of repeated amphetamine administration and withdrawal on brain reward function has relevance to both amphetamine d ependence and non-drug-induced depressions. Objectives: The purpose of this study was to investigate the effects of continuous amphetamine administrat ion and withdrawal on brain stimulation reward thresholds, and the changes that occur with repented amphetamine exposures. Methods: Rats were prepared with bipolar electrodes in the lateral hypothalamus and trained in a discr ete-trial reward threshold procedure. Then, rats underwent two separate per iods of amphetamine administration via subcutaneous osmotic mini-pumps. Res ults: Continuous amphetamine administration was associated with Towering in blain reward thresholds and decreases in response latencies. while withdra wal was associated with threshold elevations. These effects changed with su bsequent amphetamine administration and withdrawal. Conclusions: The result s of this study indicated that with the amphetamine administration regime u sed hen, rats developed increased sensitivity to the effects of acute amphe tamine administration and tolerance to the effects of amphetamine withdrawa l.