REGIONAL SEROTONIN(1A) RECEPTORS IN THE CNS OF ALCOHOL-PREFERRING ANDALCOHOL-NONPREFERRING RATS

The densities of serotonin(1A) (5-HT1A) receptors, labeled with [H-3]8 -hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), were examined in t he CNS of alcohol-naive adult male alcohol-preferring (P) and -nonpref erring (NP) rats using quantitative autoradiography. The densities of sites labeled with 2 nM [H-3]8-OH-DPAT were a) 20-30% higher in the me dial prefrontal, frontal (layers 1, 2, and layers 3-6), parietal (laye rs 3-6), and cingulate cortex; b) 35-40% higher in the retrosplenial, occipital (all layers), temporal (all layers) cortex; and c) 15% highe r in the entorhinal cortex of the P compared with the NP rat. Within t he hippocampus, significant differences between the rat lines were obs erved only in the posterior portion where the densities of [H-3]8-OH-D PAT labeled sites were a) 10-15% higher in the dorsal dentate gyrus, d orsal CAI, and dorsal CA3 regions; and b) 15-25% higher in the anterio r ventral hippocampal area and ventral dentate gyrus of the P relative to the NP line. In contrast to the above results, the densities of [H -3]8-OH-DPAT labeled sites were 15-20% lower in the dorsal, paradorsal , and median raphe nuclei of the P compared with the NP rat. No differ ences in [H-3]8-OH-DPAT binding between the rat lines were found in se veral basal ganglia, limbic, and brain stem regions. The data indicate that there are greater numbers of postsynaptic 5-HT1A receptors in ce rtain parts of the cerebral cortex and hippocampus of the P compared w ith the NP rat. In addition, the lower densities of 5-HT1A cell body a utoreceptors in the raphe nuclei suggest that there are fewer 5-HT neu rons in the raphe nuclei of the P than of the NP rat.