Facilitated acquisition but not persistence of responding for a cocaine-paired conditioned reinforcer following sensitization with cocaine

Sensitization has been hypothesized to increase the incentive salience of drug-paired conditioned stimuli and in the present study the ability of a sensitizing pretreatment with cocaine to increase responding for a drug-paired conditioned reinforcer was tested. In support of the incentive-sensitization hypothesis, sensitized rats earned more presentations of a drug-paired conditioned reinforcer during acquisition of a new response for this stimulus. By comparison, sensitization had no effect on the number of CSs earned during reversal of the contingency or following pretreatment with d-amphetamine. During reversal learning, however, sensitized rats were impaired in the extinction of the inappropriate response once the contingent CS was no longer available following presses on that lever. The results are discussed with reference to a possible role of increased incentive salience of a drug-paired CS to the formation of a habit.