The effect of d-amphetamine on operant behaviour maintained under variable-interval schedules of reinforcement.
Dose-response curves were obtained for the effects of d-amphetamine sulphate (0.1-3.2 mg/kg) on the operant performance of rats in variable-interval 4-min and variable-interval 20-min schedules of reinforcement. Response rates maintained under variable-interval 4-min were suppressed in a dose-dependent manner. Response rates maintained under variable-interval 20-min schedules tended to be elevated by low doses and suppressed by higher doses. The degree of response rate suppression was greater in the case of the variable-interval 4-min schedule. The results are consistent with the previously reported effect of d-amphetamine on the values of the two constants of Herrnstein's (1970) equation: the drug reduces the reinforcement frequency needed to maintain the half-maximum response rates (KH) and lowers the maximum response rate (Rmax) (Bradshaw et al. 1981 b). It is suggested that the effects of d-amphetamine on operant performance may involve two processes: an enhancement of motivation and a reduction of the capacity to respond.
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005508:Food Deprivation; D051381:Rats; D011919:Rats, Inbred Strains; D012055:Reinforcement Schedule
D003913:Dextroamphetamine