GRM5 and alcohol abuse: Studies in rodents show that mGluR5 signaling is involved into the reinstatement of alcohol and nicotine self-administration.7,8, In humans, we found that in ex-smokers mGluR5 DVR was related to the risk for relapse.19 Based on these results, we investigated whether mGluR5 DVR relates to the risk for relapse in alcohol use disorder.