FIGURE 1.

Timeline of the experiments. After 4 weeks of habituation to the vivarium, male Sprague–Dawley rats were given intermittent access to a 10% alcohol in a two‐bottle choice procedure. After 3 weeks of alcohol exposure, the compulsive nature of drinking behavior was assessed over successive challenge sessions during which the propensity of each individual to persist in drinking alcohol despite adulteration with quinine (session 10) or an alternative reward, saccharin (session 14), was measured. Three subpopulations, namely Adulteration‐Alternative reward Resistant (AAR), Intermediate and Sensitive (AAS), were characterized by K‐means clustering. Rats were re‐baselined in the intermittent two‐bottle choice procedure for 3 weeks, and the effect of baclofen (1 and 1.5 mg/kg) on voluntary alcohol drinking was measured for the entire population following a Latin square within‐subject design with a baseline session between treatments (baclofen/alcohol intake, sessions 23 to 27). Rats were then re‐baselined for 9 weeks, and the effect of baclofen on the persistence in alcohol drinking despite adulteration for the AAR and AAS subpopulations was assessed following a between‐subject design (baclofen/alcohol adulteration, session 54). Lastly, rats were re‐baselined before being sacrificed (session 62) and their brains harvested for posterior molecular analysis. Hab: habituation; Mol: molecular analysis; s: session; Sacch choice: saccharin choice