Effect of amphetamine on behavior maintained by sucrose: interaction of reinforcement schedule and food restriction.

A multiple schedule (Mult FR 10 VI 30") was employed to examine the interaction of reinforcement schedule and food restriction on amphetamine's effects on lever pressing behavior. High response rates were observed in fixed ratio (FR) 10 components. Significantly lower response rates were observed under the variable interval (VI) 30" schedule. In the nonrestricted feeding condition, significant decreases in high rate FR 10 responding occurred after administration of 1.0 mg/kg amphetamine while lower rates under the same schedule were increased by 0.30 and 1.0 mg/kg amphetamine. In contrast, VI 30" responding was minimally effected at any amphetamine dose. Food restriction resulted in significant increases in responding in both schedule components. Under food restriction, significant decreases in responding were observed only in the FR 10 components at the highest amphetamine dose. The data indicate that amphetamine produced rate-convergent effects and the susceptibility of the animal to these effects was dependent on the schedule of reinforcement and food restriction.