Competition Between Conditioned Rewards: Novelty vs. Cocaine

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DESCRIPTION (provided by applicant): The associations formed between the physiological effects of abused drugs and cues in the drug-taking environment are critical factors in the acquisition, maintenance, and relapse of drug-taking behavior. Because these conditioned associations exert some control over choice behaviors involving drug reward, behavioral intervention strategies may need to employ techniques to reduce the influence of conditioned drug reward over choice behaviors. For example, such programs may benefit by providing new learning opportunities to compete with conditioned drug reward. Access to novelty reward might provide an alternative learning history with the potential to compete with conditioned cocaine reward. By studying this competition, we hope to enhance the development of comprehensive drug abuse treatment programs. Therefore, one of the objectives of this proposal is to test whether a change in learning history can compete with conditioned drug reward for control over choice behavior. The experiments proposed in this application will help meet our goal by systematically investigating the extent to which novelty conditioned reward can compete with conditioned cocaine reward over a range of cocaine doses. We will also assess whether unpaired cocaine exposure is important for this competition. Additionally, we will determine whether novelty competition can be maintained over time. This competition will be investigated using a place conditioning procedure with cocaine and novelty. Initially, rats will be conditioned with cocaine to prefer one side of an unbiased place conditioning apparatus. In the subsequent phase, half of the rats will have repeated access to a novel object on their originally unpaired (no-drug) side. Both groups will then be tested on separate days for preference in a drug-free state and in the cocaine-drug state. Preliminary data indicates that access to novelty can shift a preference away from the cocaine-paired environment during drug-free testing and this shift remains even when rats are given an ensuing test in the cocaine-state. Thus, the conditioned rewarding effects of novelty changed choice behaviors motivated by drug reward. We expect that this competition will persist with higher doses of cocaine, when cocaine-paired cues are maintained, and at longer testing intervals.