A variant on the kappa opioid receptor gene (OPRK1) is associated with stress response and related drug craving, limbic brain activation and cocaine relapse risk

Stress increases drug craving and relapse risk. The kappa opioid receptor gene (OPRK1) mediates stress responses. Here, we examined whether the OPRK1 rs6989250 C4G affects stress-induced cocaine craving and cortisol responses, subsequent cocaine relapse risk and the neural response to stress using functional magnetic resonance imaging (fMRI) in cocaine dependence. Sixty-seven treatment-engaged, abstinent cocaine-dependent African-Americans were genotyped (CG: N=10; CC: N=57) and participated in a 3-day experiment in which they were exposed to personalized script-driven imagery of stress, drug cues and neutral scenarios, one condition per day, randomly assigned and counterbalanced across subjects. Repeated measures of craving and cortisol were obtained. The subjects were followed prospectively for 90 days to assess relapse risk. A follow-up preliminary fMRI experiment assessed neural responses to stress, drug cue and neutral conditions in matched CG (N=5) and CC (N=8) subgroups. We found greater stress-induced craving (P=0.019), higher cortisol during stress and cue relative to the neutral condition (P's<0.003), and increased cocaine relapse risk (P=0.0075) in the CG compared with the CC group. The CG relative to the CC group also showed greater activation of limbic and midbrain regions during stress and cues relative to the neutral condition with additional stress-induced activation in the right amygdala/hippocampus (P<0.05, wholebrain corrected). These results suggest that OPRK1 is associated with stress-induced craving and cortisol, hyperactive hypothalamus/thalamus-midbrain-cerebellum responses, and also associated with greater subsequent cocaine relapse risk. Future studies to replicate these findings in a larger sample size are warranted.