DIABETES ALTERS MU-OPIOID AND KAPPA-OPIOID BINDING IN RAT-BRAIN REGIONS - COMPARISON WITH EFFECTS OF FOOD RESTRICTION

Diabetic rats display changes in opioid pharmacology and brain regiona l levels of opioid peptides and prodynorphin mRNA. Previous investigat ions of opioid receptor binding, carried out in whole-brain homogenate s, have, however, failed to detect changes. In the present study, quan titative autoradiography was used to measure mu and kappa opioid recep tor binding in discrete brain regions of streptozotocin-treated diabet ic rats. Measurement was limited to regions that previously displayed opioid binding changes in chronically food-restricted rats, since our primary aim is to identify brain mechanisms that mediate adaptive resp onses to persistent metabolic need and adipose depletion. Diabetics di splayed strong trends or statistically significant changes which match ed seven of the thirteen binding changes observed in food-restricted r ats. In no case did diabetics display changes in the opposite directio n. The two statistically significant changes common to food-restricted and diabetic rats are increased kappa binding in the medial preoptic area and decreased mu binding in the lateral habenula. The possible fu nctional significance of these changes is discussed.