Action of caffeine, d-amphetamine, diazepam and imipramine in a dynamic behavioural situation

A study has been made of how the chronic administration of caffeine, d-amphetamine, imipramine and diazepam affect rat behaviour in four successive trials in which the contingency for food delivery was switched from one lever where responses were previously reinforced to the other lever where responses had no programmed consequences (reversal). A complete extinction in the first reversal was obtained with diazepam 0.3 mg/kg/day. Caffeine (6 and 18 mg/kg/day) had no effect in the first reversal and damaged rat performance in the successive reversals. Imipramine (0.6 and 4 mg/kg/day) had the same effect but only in the fourth reversal. Amphetamine (0.16 and 0.7 mg/kg/day) caused a clear damage of rat performance only in the third and fourth reversals.