Effects of chronic food restriction on mu and kappa opioid binding in rat forebrain: a quantitative autoradiographic study

Abstract It was previously observed that chronic food restriction lowers the threshold for lateral hypothalamic self-stimulation in a manner that is reversible by μ- and κ-selective opioid antagonists. The present quantitative autoradiographic study was designed to investigate whether chronic food restriction alters regional μ and κ opioid binding in brain. [ 3 H]DAGO (μ) and μ//gd blocked [ 3 H]BMZ (κ) binding were analyzed in 34 brain regions from the medial prefrontal cortex to posterior hypothalamus. Significant reductions in μ binding were observed in caudal portions of the medial and lateral habenula, and the basolateral and basomedial nuclei of the amygdala. κ binding was similarly reduced in medial habenula. Large increases in κ binding were observed in the bed nucleus of the stria terminalis, ventral pallidum, and medial preoptic area. The possible involvement of these changes in the sensitization of reqard by food restriction is discussed.