Compulsive behaviors, including excessive eating, gambling, shopping, exercising, or drug-taking, can develop over time in individuals without other psychopathology. Although compulsive behavior is marked by excessive engagement in a particular behavior, animal models of compulsive behavior suggest that another defining feature is behavior that is disconnected from reinforcer delivery. Thus, people may gamble compulsively even though they do not win often, or shop excessively even when they may not use what they have purchased. Our hypothesis is that these types of reinforcer- disconnected behaviors result when both operant (instrumental, goal-tracking) and respondent (Pavlovian, classical, sign-tracking) conditioning processes converge on the same behavior. In addition, individuals must be sensitized to dopamine, and the compulsive behavior is more likely to occur in the presence of a D3/D2 agonist acting on the sensitized dopamine receptors. We will test this hypothesis in three behavioral models: 1) quinpirole-induced responding for stimuli associated with cocaine;2) quinpirole-induced responding for water in the presence of water;and 3) quinpirole as an occasion setter for either cocaine or water-reinforced behavior. The behavioral pharmacology of these models will be tested with various dopamine agonists and antagonists, and the roles of sensitization, goal-tracking, and sign-tracking will be studied. Understanding the environmental, behavioral, neurochemical, and pharmacological aspects of compulsive disorders will hopefully contribute to the development of treatments for these debilitating disorders. PUBLIC HEALTH RELEVANCE: The purpose of this proposal is to determine various environmental and neurochemical contributors to compulsive behavior (e.g., excessive gambling, shopping, eating, sexual behavior, and drug-taking). Our hypothesis, that compulsions result when the same classically conditioned and operantly conditioned behavior is established in the presence of sensitized dopamine receptors and stimulation of dopamine receptors, will be tested in three rat models in this research effort. Evaluation of the ability of selective dopamine receptors, as well as silencing the RNA for the D3 receptor, to modify the compulsive behavior should help point towards possible pharmacological treatment of these disorders, and understanding of the setting conditions will suggest behavioral therapy and prevention approaches.