The effects of fenfluramine on schedule-induced drinking in rats.

The lever pressing of rats was maintained by a fixed-interval 60 sec schedule of food reinforcement. Water bottles were available during sessions and high levels of schedule-induced drinking developed. Both fenfluramine (0.5, 1.0, 2.0, 4.0, 8.0 mg/kg) and d-amphetamine (0.25, 0.5, 1.0, 2.0 mg/kg) produced dose related decreases in this drinking with d-amphetamine approximately four times as potent as fenfluramine. d-Amphetamine produced large increases in overall rates of lever pressing and greatly decreased the duration of postreinforcement pauses. Fenfluramine exerted similar actions but at all doses studied these effects were much less than the effects of d-amphetamine on these measures.