CENTRAL 5-HT3 RECEPTORS IN P AND IN AA ALCOHOL-PREFERRING RATS - AN AUTORADIOGRAPHIC STUDY

Considerable evidence exists for an involvement of serotonergic mechan isms in the control of alcohol consumption. In the present study, an e xtensive 5-hydroxytryptamine (5-HT3) receptor autoradiographical inves tigation was performed using two genetically selected rat strains, alc ohol preferring (P) and Alko alcohol (AA) alcohol-preferring rats, as well as the corresponding alcohol nonpreferring (NP) and Alko nonalcoh ol (ANA) alcohol-nonpreferring rats. The aim was to determine if there are any differences in 5-HT3 binding levels that may illuminate mecha nisms of alcohol preference in these animals. For quantitating 5-HT3 b inding sites, [H-3]S(-)zacopride (0.5 nM) was used. Non-specific bindi ng was measured in the presence of granisetron 10(-6) M. The [H-3]S(-) zacopride binding density was measured in two subregions of the amygda loid nucleus, frontal cortex, piriform cortex, cingulate laminae, pari etal anterior cortex, parietal medial cortex, hippocampus CA1, hippoca mpus CA3, and entorhinal cortex. In all the brain areas investigated, the results showed no differences between AA and ANA rats. In P rats, compared to NP controls, there was a 30% lower 5-HT3 binding level in the lateral nucleus and the posteromedial cortical nucleus of the amyg dala. These findings suggest that the expression of high alcohol prefe rence in genetically selected P and AA rats is not associated with a g eneral alteration of central 5-HT3 receptors, although a lower 5-HT3 r eceptor level in the amygdala of P rats may contribute to the phenotyp e of this strain of animals. (C) 1998 Elsevier Science Inc.