Hence, these genetic analyses suggest that variations in GABA receptors are involved in both alcohol dependence and nicotine dependence. As described earlier, GABA, as an inhibitory neurotransmitter, prevents nerve signals from being propagated across neurons. Accordingly, dysfunction in GABA receptors may lead to excess activation of neurons (i.e., central nervous system hyperexcitability)—an assumption that is consistent with the observed contribution of differences in the GABRA2 gene to variability in the P300 brain waves described above. Some authors have suggested that these electrophysiological differences may be associated not only with alcohol dependence but with a broader spectrum of drug dependence, including nicotine dependence, and other behavioral disorders (Iacono et al. 2002).
