Subjects’ weights across the experimental protocol. Each time-point is an average of 3–5 sessions within the same phase (i.e., 3 acquisition sessions). Weights were evaluated during acquisition of bottle choice ethanol self-administration and during ethanol re-exposures (R) following a treatment (T) period with vehicle (Veh), the 5-HT2A antagonist M100907 (M100, 1 mg/kg, i.p.) and/or ayahuasca (100 mg/kg, i.g.). Data are shown as mean±SEM.