Dose responses of single, acute administration of Mesyl Salvinorin B (MSB, 0, 0.1, 0.3, 1 or 3 mg/kg) alone or combined with naltrexone (NTN, 0, 0.3 or 1 mg/kg) on reducing 15% alcohol intake (A) and alcohol preference (B) in both male and female mice (n=5–8) after 3-week chronic escalation drinking. Data were collected at the 4-hour time point on the baseline and testing day (24 hours later) and are expressed as a percentage of baseline alcohol intake to account for the differences in baseline that contribute to variation between experiments. **p<0.01 vs. control (both MSB and NTN at 0 mg/kg); ## p<0.01 between treatment groups (see the statistical analysis in Supporting Information section).