G118 allele-carriers tested positive for an alcohol use disorder, and that the G118 allele was associated with increased self-reports of drinking in order to enhance positive affect (Miranda et al., 2009). Functionally, G118 allele-carriers have demonstrated an increased BOLD response in fMRI in the orbitofrontal cortex, ventromedial prefrontal cortex, and striatum in response to alcohol and alcohol-related cues (Filbey et al., 2008). Additionally, a significant increase in dopamine receptor sensitivity, as measured by increases in apomorphine-induced growth hormone secretion, was found in G118 allele-carrying alcoholics following one week of alcohol abstinence (Smolka et al., 1999).
