Regional CNS densities of serotonin and dopamine receptors in high alcohol-drinking (HAD) and low alcohol-drinking (LAD) rats.

The densities of subtypes of serotonin (5-HT) and dopamine (DA) receptors were determined in the CNS of male alcohol-naive HAD and LAD lines of rats. Autoradiographic studies were undertaken to measure the densities of (a) 5-HT1A sites labelled with 2 nM [3H]8-OH DPAT, (b) 5-HT2A sites labelled with 2 nM [3H] ketanserin, (c) D1 sites labelled with 1 nM [3H]SCH23390, and (d) D2 sites labelled with 20 nM [3H]sulpiride. Membrane binding, using tissue combined from the olfactory bulb, olfactory tubercle, and nucleus accumbens, was carried out to determine Kd and Bmax values for the binding of 0.25-8.0 nM [3H]7-OH DPAT to D3 sites. Among the 14 regions measured for densities of 5-HT1A sites, no interline differences were found in the cerebral cortical regions or in the septal nuclei; however, within the hippocampus, 15-20% lower binding of [3H]8-OH DPAT was observed in the posterior dorsal CA3 and dentate gyrus of the HAD line. There were no interline differences in any of the 10 regions examined for [3H]ketanserin binding to 5-HT2A sites, or in the densities of D1 and D2 sites in the mesolimbic and nigrostriatal DA systems, except for a 35% higher density of D2 sites in the substantia nigra pars compacta of the HAD line. There were no interline differences in the Kd or Bmax values for [3H]7-OH DPAT binding to D3 sites. Overall, these results indicate that no marked interline differences are evident in the densities of 5-HT1A, 5-HT2A, D1, D2, and D3 receptors within the mesolimbic system that could be associated with the disparate alcohol drinking behaviors of the HAD and LAD rats.