Compulsive binge eating of highly palatable foods is a frequently observed behavior in a wide variety of eating disorders including anorexia nervosa, bulimia nervosa, and obesity. As opiates affect taste preferences and consumption of highly palatable foods in animals, compulsive binge eating of such foods in humans may be related to abnormal function of the endogenous opioid system. This proposal consists of complementary animal and human studies aimed at defining the relationship between opioid system function and taste and food preferences. The effects of receptor- specific opioid agonists for mu, kappa, and delta receptors on taste preferences and diet selection in rats will be tested using intracerebral microinjection techniques. Rats will be tested in nondeprived and schedule-deprived paradigms. The data obtained in these experiments will provide the basis for a receptor- specific, site-specific mechanism for central opioid modulation of taste preference and diet selection in normal and abnormal feeding situations in animals. The effects of acute changes in opioid system function on human taste responses and diet selection will be tested in compulsive binge eaters ranging from anorectic to obese weigth ranges and non-binge-eating controls of similar weight. Each subject will be tested for taste responses to stimuli consisting of milkshakes with a wide range of sugar and fat content during peripheral infusions of naloxone, butorphanol, and saline. Taste response data will be analyzed using the Response Surface Method. Food selection and intake in each of these conditions will also be measured. Results from this experiment will establish the importance of opioid system function in the taste responses and food choices of obese and eating disordered humans. Because the design has controls for body weight status and binge-eating status, the relationship of each of these states to abnormal opioid function will be detected. Thus, these experiments will provide data on the basic opioid mechanisms involved in taste preferences and their relevance to human pathology. A better understanding of this mechanism may suggest more specific treatment interventions for eating disorders as well as other addictive states in the future.
