Binding of serotonergic ligands to brain membranes of alcohol-preferring AA and alcohol-avoiding ANA rats

The alcohol-preferring AA rats have higher concentration of 5-hydroxytryptamine (5-HT) in the brain than the alcohol-avoiding ANA rats. In the present study, the 5-HT₁, 5-HT₂, and 5-HT₃ receptors were studied with [³H]5-HT, [³H]ketanserin, and [³H]LY278584, respectively, in membrane homogenates from different brain regions of both rat lines using in vitro binding assays. No differences in the 5-HT₁ and 5-HT₂ receptor binding in the brainstem, hippocampus, frontal cortex, and hypothalamus or in the 5-HT₃ receptor binding in the nucleus accumbens, amygdala, hippocampus, and frontal cortex were observed between the ethanol-naive animals of the rat lines. In rats given the opportunity to voluntarily consume alcohol, there was a tendency to increase 5-HT₁ binding in the ANA rats, which tendency was, however, also found in their ethanol-naive controls subjected to the same handling and behavioral tests as the ethanol-experienced animals. The results do not, however, indicate that any genetic modifications of the 5-HT receptor-binding sites have occurred in the process of the selective breeding of AA and ANA rats for alcohol preference and avoidance, respectively.