Endogenous opioids and striatal dopamine have been implicated in cue-induced alcohol craving and have been hypothesized to play a role in goal-directed, as opposed to habitual, alcohol use. This initial study examines dorsal and ventral-striatal functional connectivity during alcohol cue processing as a function of the A118G single nucleotide polymorphism (SNP) of the mu opioid receptor (OPRM1) gene.
Seventeen individuals with alcohol dependence (6 females; 90% Caucasian; mean age = 29.4) underwent blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) while performing an alcohol taste-cues task. Psychophysiological interaction (PPI) analyses investigated associations of the OPRM1 genotype with ventral and dorsal striatum functional connectivity, using the ventral striatum and the caudate as the seed region, respectively.
Compared to A-allele homozygotes, G-allele carriers of the OPRM1 gene showed (a) greater activation of the insula and orbitofrontal cortex and (b) stronger negative fronto-striatal functional connectivity for both ventral and dorsal striatal seed regions during processing of alcohol versus water cues.
These preliminary findings suggest that, relative to A-allele homozygotes, G-allele carriers show unstable frontal regulation over reward and/or habit-driven inputs from the striatum resulting from greater reward sensitivity combined with limited self-control resources.