Effects of d-amphetamine and d-fenfluramine on performance of rats in a food maze.

d-Amphetamine and d-fenfluramine caused different patterns of disruption in a learned maze performance reinforced with food. A 0.8 mg/kg dose of amphetamine increased correct and incorrect (errors) alley entrances as well as earned reinforcers consumed. Larger doses (1.6-3.2 mg/kg) decreased correct responses, increased errors, and resulted in earned reinforcers not being consumed. Metergoline pretreatment did not reverse these deficits. d-Fenfluramine (1.5 and 3.0 mg/kg) reduced correct responses dose- relatedly with a slight increase in errors after the larger dose; all earned reinforcers were consumed. Pretreatment with metergoline reversed the deficit in correct responses but not the errors. Combinations of d-amphetamine and d-fenfluramine produced greater deficits than each drug separately, with fewer correct responses and an increase in reinforcers earned but not consumed. Metergoline pretreatment before the combination did not reverse these effects but increased alley entrances scored as errors. The results indicate that the d-fenfluramine but not the d-amphetamine deficit relates to a 5-hydroxytryptamine (5-HT) mechanism. Furthermore, the enhanced effect of the combination appears to relate to drug interactions not dependent upon a 5-HT component.