BETA-ENDORPHIN AND DYNORPHIN ABNORMALITIES IN RATS SUBJECTED TO EXERCISE AND RESTRICTED FEEDING - RELATIONSHIP TO ANOREXIA-NERVOSA

Exercise and the endogenous opioids have been linked to anorexia nervo sa. This investigation determined the effects of the weight-loss syndr ome induced by voluntary exercise (22.5 h/day) in food-restricted rats (1.5 h/day food access) on the endogenous opioids. The animals were t ested under resting-fed and 2-deoxy-D-glucose (2DG) stimulated conditi ons. Weight-matched, freely fed exercised and ad libitum fed unexercis ed groups served as controls. Specific opioid abnormalities were found in the syndrome. These included a basal elevation in plasma beta-endo rphin, which was abnormally suppressed by 2DG, and 2DG-induced elevati ons in arcuate hypothalamic beta-endorphin content and supraoptic hypo thalamic dynorphin-A content. None of these changes occurred in contro ls. Finally, it was found that short-term moderate exercise itself chr onically reduced adenohypophysial beta-endorphin content and elevated supraoptic dynorphin-A content. The relationship of the syndrome's hyp erendorphinism to the hypothalamo-pituitary-adrenal axis and the auto- addiction hypothesis of anorexia nervosa was considered, as was the si gnificance of the supraoptic dynorphin-A abnormality to the hypothalam o-neurohypophysial system. The differential sensitivity of the supraop tic dynorphin-A system compared to the arcuate hypothalamic beta-endor phin system to moderate exercise was also discussed.