Glycine receptor expression in the forebrain of male AA/ANA rats.

Ethanol is known to directly interact with the glycine receptor (GlyR). GlyRs are membrane proteins and are constituted as either alpha-homomers or alpha-beta heteromers with a subunit stoichiometry of 2 alpha 3 beta. Previous studies by our group have suggested a role for GlyRs and its endogenous ligands glycine and taurine in the mesolimbic dopamine activating and reinforcing effects of ethanol. Here we use quantitative PCR (qPCR) to compare the relative GlyR expression in Alko Alcohol/Non-Alcohol (AA/ANA) rats. These animals have been selectively bred to create distinct populations regarding alcohol consumption and preference, presumably mainly due to genetic differences. The aim of this study was to examine the relative gene expression of GlyR subunits (alpha1-3 and beta) in different brain areas and relate it to alcohol consumption. The hypothesis was that AA/ANA rats are differently disposed to ethanol consumption due to their GlyR set-ups and/or compositions. Results from the present study indicate that alpha2 is the most widely expressed alpha-subunit in the forebrain regions and that the alpha 2 beta-heteromer seems to be the most common subunit composition in this part of the CNS. Despite displaying different drinking behaviours the anticipated differences in mRNA expression were few. However, correlations found between alcohol consumption and/or preference and GlyR expression support a role for GlyRs in alcohol consumption. Tentative differences between AA and ANA animals related to GlyR transmission could therefore lie in, for example, the regulation of the levels of the endogenous ligand(s) for the receptor or in mechanisms downstream to GlyR activation.