a Timeline of Exp. 4. b FR1 oxycodone self-administration training and testing (6-h sessions): Number of oxycodone infusions (0.1 mg/kg/infusion) after (–)-OSU6162 pretreatment (0, 7.5, 15 mg/kg). c PR oxycodone self-administration training and testing: Number of oxycodone infusions and final ratio after (–)-OSU6162 pretreatment (0, 7.5, 15 mg/kg). Data are mean ± SEM, n = 6 males/7 females that previously participated in Exp. 2. See Fig. S1 for individual data.