DESCRIPTION (provided by applicant): The motivation and desire to obtain a reward underlies many behaviors ranging from natural incentives such as the intake of food to the pharmacological modulation of brain circuitry involved with drugs of abuse. Substantial evidence suggests that the mesolimbic dopamine (DA) system plays a key role in modulating the neurochemical circuitry involved in reward pathways. Alterations in DA activity may underlie individual differences in reward sensitivity as well as the propensity to pursue rewarding stimuli despite undesirable consequences. Moreover, recent evidence suggests that a disturbance in one system affecting reward changes the responsiveness of other reward-related systems. Given that DA influences the properties of a reward, the goal of this proposal is to measure the specific behavioral and neurochemical changes that occur following experimental manipulation of food and drug reward pathways. First, I will use conditioned place preference to determine if food restricted rats will select an environment associated with food over an environment associated with cocaine. Second, I will use 11 C-raclopride and microPET, in combination with AMPT, to measure changes in D2 receptor number induced by chronic food restriction and/or cocaine use.