Conditioned taste aversion learning: implications for animal models of drug abuse

Drugs of abuse are typically discussed in terms of their rewarding effects and how these effects mediate drug taking. However, these drugs produce aversive effects that could have an important role in the overall acceptability of a drug and its likelihood of being self-administered. Rewarding and aversive effects, then, could be interpreted as separate behavioral effects, with the balance of the two determining overall drug acceptability. Interestingly, the role of aversive effects on drug acceptability in the self-administration preparation has received limited attention in this context. This chapter examines the aversive effects of drugs and discusses their role in drug taking. If these aversive effects serve a protective function, manipulations that alter or decrease these effects could have implications for drug taking. Several factors have been reported to alter conditioned taste aversion (CTA) learning, a preparation used in the assessment of the aversive effects of drugs in general. Two of these factors, drug history and strain, are reviewed here. By reviewing these, we intend to demonstrate the protective nature of aversive effects in the initiation and escalation of drug taking and to provide evidence that reductions in aversive effects could produce changes in patterns of drug self-administration that could lead to an increased vulnerability to abuse drugs by altering the reward-aversion balance. The aim of this chapter is not to question the importance of rewarding effects in self-administration but rather to provide evidence that aversive effects are an important factor that needs to be considered in discussions of drug-taking behavior.