Rate-dependent effect of amphetamine in rats: Extension to between-subjects effect

Abstract
Following either variable-interval or fixed-interval training, 20 rats received both 0.5 and 2.0 mg/kg of amphetamine. For both schedules, amphetamine decreased response rates of high-rate subjects and increased those of low-rate subjects. Within-subject analysis of fixed-interval rates revealed the same rate-dependent effect. It is suggested that the between-subject and within-subject effects may have the same basis.