Conditioned Taste Aversions and the Regulation of Drug-Taking Behavior

INTRODUCTION Considerable progress in the understanding of behavioral factors in drug dependence was made after methods were described for inducing animals to administer drugs to themselves. This development led to a new emphasis on the direct study of drug-taking behavior under controlled conditions, and it very effectively complemented the information obtained with the traditional pharmacological and psychiatric approaches, as well as challenging some common assumptions. Researchers studying drug self-administration in animals have frequently interpreted their findings within an operant conditioning framework where the behavior is said to be maintained by positive reinforcing effects of the drugs. Many people have found it difficult to accept that some of the same self-administered drugs are extremely effective agents for producing the phenomenon called conditioned taste aversion (CTA). Drugs such as amphetamine, morphine, and chlordiazepoxide, which are known to serve reinforcing stimulus functions in self-administration experiments are also able to serve as the unconditioned, presumably aversive, stimulus in CTA studies. These superficially "paradoxical" effects need not be considered surprising in view of other evidence that the same nondrug stimulus can serve either reinforcing or aversive functions according to the circumstances (Morse and Kelleher, 1977), and in view of the multiple actions exerted by nearly all drugs.