Effects of prior drug experience on the establishment of taste aversions in rats.

Groups of food and water deprived rats were injected with either 2 mg/kg d-amphetamine, 9mg/kg dl-fenfluramine or isotonic saline immediately after the first presentation of a 25 percent solution of condensed milk for a 30 min period. When animals were tested for aversion to condensed milk 8 days later both drugs were found to cause a highly significant decrease in total amounts drunk; in contrast saline injected animals showed significant increases in the amount drunk. However, it was found that the development of a conditioned taste aversion could be markedly attenuated or abolished altogether by providing groups of animals with experience of both drugs prior to aversion establishment, and that the degree of attenuation of aversion was proportional to the amount of prior experience. Novelty of drug administered would seem to be a critical variable in the establishment of taste aversions. The results are discussed with reference to some of the paradoxical aspects of drug induced taste aversions.