Flavour aversions conditioned by dl-fenfluramine: a volume independent mechanism.

Fenfluramine, a clinically used anoretic agent, is known to act as a potent unconditioned stimulus in the establishment of a conditioned flavour aversion (CFA). Here we demonstrate that dl-fenfluramine supports the development of a CFA to a novel flavour when drug administration precedes the CS (reverse pairing), although several such UCS/flavour pairings are required under our conditions. In this situation, because fenfluramine exerts a strong anorectic effect, the animals drink little of the flavoured solutions. Artificial reduction of the volume of solutions drunk during conditioning also had no effect on the magnitude of the aversion with either forward or reverse pairings of the UCS and CS. These results suggest an alternative explanation to the idea that a fenfluramine-induced CFA arises as a secondary consequence of delayed stomach emptying.