Effects of CAB2-015 or BAK4-54 on oxycodone self-administration dose-response curve in rats. A: Pretreatment with CAB2-015 (10 mg/kg, i.p.) or BAK4-54 (10 mg/kg, i.p.) significantly shifted the dose-response curve downward; B: Calculated oxycodone intake, indicating that CAB2-015 or BAK4-54 significantly shifted the dose-intake curves downward. *p<0.05, **p<0.01, compared to the vehicle group. N=7-8/group.