Other gene variants also have been associated with the risk for alcoholism, including genes encoding many of the subunits of a receptor for the brain signaling molecule (i.e., neurotransmitter) γ-aminobutyric acid (GABA). This GABAA receptor consists of five subunits, and studies have found that certain alleles of several subunit genes can influence the risk for alcoholism and other addictions, as well as of conduct disorder symptomology and can modify electrophysiological traits related to these disorders. For example, many (although not all) studies have implicated alleles of the GABRA2 gene, which encodes the α2 subunit of the GABAA receptor, in alcoholism risk (for more information, see the article by Borghese and Harris, pp. 345–353). Other GABAA receptor subunit genes also have been implicated, including GABRG1, GABRA1, GABRG3, GABRR1, GABRR2, and GABRB3. Both physiological and molecular evidence indicates that GABAA receptors are affected by alcohol and participate in many processes relevant to addiction, and studies in rodents have provided further evidence of this involvement. Overall, however, the effects even of the best studied of these genes, GABRA2, seem to be small. Although
