RESUMO
The purpose of this study was to assess the effects of the psychomotor stimulant fencamfamine (FCF) on the operant response rate and on the parameters k and R(e) of Herrnstein's hyperbola. In the first experiment, rats were trained on a multiple variable interval (VI) schedule. Each rat was then given two i.p. injections of a randomly assigned FCF dose (0.0, 0.88, 1.75 and 3.5 mg/kg) at 48 h intervals. The overall response rate, the individual VI response rate, and the k and R(e) parameters of the hyperbola equation were calculated. In the second experiment, two groups of animals were trained drug-free on the same schedule. Afterwards, the animals in one group received six i.p. injections of 1.75 mg/kg FCF at 48 h intervals while subjects in the other group received vehicle injections, 15 min before each experimental session. Seven days after the last injection, a challenge dose (0.88 mg/kg) of FCF was administered and performance was measured. FCF increased overall response rate and decreased R(e) without changing k. Previous exposure to FCF did not induce sensitization of these measures. These results indicate that FCF has similar effects on k and R(e) as those produced by other indirect dopaminergic agents, and supports previous findings suggesting FCF as a potential drug of abuse.