EFFECTS OF CHRONIC FOOD RESTRICTION ON MU-OPIOID AND KAPPA-OPIOID BINDING IN RAT FOREBRAIN - A QUANTITATIVE AUTORADIOGRAPHIC STUDY

It was previously observed that chronic food restriction lowers the th reshold for lateral hypothalamic self-stimulation in a manner that is reversible by mu- and kappa-selective opioid antagonists. The present quantitative autoradiographic study was designed to investigate whethe r chronic food restriction alters regional mu and kappa opioid binding in brain. [H-3]DAGO (mu) and mu/delta blocked [H-3]BMZ (kappa) bindin g were analyzed in 34 brain regions from the medial prefrontal cortex to posterior hypothalamus. Significant reductions in mu. binding were observed in caudal portions of the medial and lateral habenula, and th e basolateral and basomedial nuclei of the amygdala. kappa binding was similarly reduced in medial habenula. Large increases in kappa bindin g were observed in the bed nucleus of the stria terminalis, ventral pa llidum, and medial preoptic area. The possible involvement of these ch anges in the sensitization of reward by food restriction is discussed.