Comparison of the effects of D-amphetamine on FI and DRL schedule performance of self-stimulating rats.

Six rats bar-pressed for intracranial self-stimulation in a Skinner box on fixed interval and differential reinforcement of low rate schedules with an interval parameter of 1.3 s. After amphetamine timing efficiency was reduced immediately on both the schedules; it recovered after 60 min on the DRL schedule but not within 120 min on the FI schedule. Response rates increased on both the schedules. The increased response rates correlated with the low efficiency on the DRL but not on the FI schedule. The selective sparing of DRL performance is in line with the similarity between the effects of amphetamine and frontal cortical lesions.