A within-subject analysis of d-amphetamine exposure on delay discounting in rats

Studies concerning the relation between stimulant drug exposure and subsequent delay discounting (impulsive choice) have resulted in mixed findings that could be related to the type of stimulant drug exposure or the use of between-subject comparisons. The purpose of the present study was to examine effects of prior d-amphetamine exposure on subsequent delay discounting using a within-subject assessment. Two groups of rats were trained under a discrete-trials choice procedure until delay discounting was stable. One group of rats then received repeated administration of 3.0 mg/kg d-amphetamine in their home cage for 14 consecutive days, while the other group received saline. After a three-week drug-free period, delay discounting was reassessed. No significant differences in area under the curve within (before or after drug exposure) or between (saline or d-amphetamine) groups were found. Thus, delay discounting was not systematically affected following termination of repeated 3.0 mg/kg d-amphetamine exposure in the present experimental arrangement. The current results, coupled with past research, indicate that there may be a distinction between cocaine exposure and d-amphetamine exposure on subsequent delay discounting; however, within-subject comparisons of cocaine exposure on delay discounting are warranted.