Organisms engage in feeding behavior under different circumstances. These include spontaneous intake regulating body weight and intake in reponse to such homeostatic challenges as food deprivation or the loss of glucose or fat energy sources. Intake increases also occur in relation to palatable, hedonic or taste qualities of the food. Endogenous opioid peptides (enkephalins, endorphins) and their receptors (mu, delta and kappa) in the brain are intimately involved in stimulating these different types of feeding behavior. Specific brain sites, including the nucleus accumbens and ventral tegmental area, are places where opioid agonists stimulate feeding behavior as well as mediate other reward and addictive behaviors. Advanced neuroanatomical and neurochemical techniques have mapped the intrinsic neuronal circuitry interconnecting these brain areas as well as extrinsic connections with sensory and montor areas controlling feeding behavior. The goals of this proposal are to systematically study these receptor substrates within and between the nucleus accumbens and ventral tegmental area by using selective mu and delta opioid agonists to stimulate feeding, and then determine whether pharmacological anatagonists of other specific neurochemical receptors (opioid, dopamine, GABA, excitatory amino acids) block these responses. This approach identifies specific neuroanatomical and neurochemical circuits within the brain mediating feeding as an important hedonic and homeostatic response as well as having potential implications for the understanding of reward and addiction
