QUANTITATIVE AUTORADIOGRAPHY OF MU-OPIOID RECEPTORS IN THE CNS OF ALCOHOL-NAIVE ALCOHOL-PREFERRING P AND ALCOHOL-NONPREFERRING NP RATS

The densities of mu-opioid binding sites in the CNS of alcohol-naive a dult male P and NP rats (N = 9 each line) were examined using quantita tive autoradiography. Coronal sections (20 mu m) were prepared from fr ozen brains and incubated in 5 nM [H-3]DAMGO to label mu-opioid recept or sites. Nonspecific binding was determined in the presence of 1 mu M DAMGO. The amount of [H-3]DAMGO binding was (a) 20-25% higher in the olfactory tubercle, nucleus accumbens shell and core, and basolateral and lateral amygdaloid nuclei; (b) 15% higher in the lateral septal in termediate nucleus and caudate-putamen patches; and (c) 10-30% lower i n the pyramidal and radiatum layers in the CA1 region of the anterior dorsal hippocampus, ventral dentate gyrus and CA1 pyramidal layer of t he posterior hippocampus, and posterior medial cortical amygdaloid nuc leus of the P compared to the NP rat. No line differences were found i n any of the other regions examined (e.g., the cerebral cortical subre gions and layers, thalamic nuclei, ventral tegmental area, ventral pal lidum, lateral hypothalamus, other regions of the hippocampus, and sev eral subcortical structures). The innate differences in the amount of binding to mu-opioid recognition sites in certain limbic structures, s uch as the nucleus accumbens, amygdala, and olfactory tubercle, of the P and NP lines may be factors contributing to their disparate alcohol drinking characteristics. (C) 1998 Elsevier Science Inc.