Dissociation of buprenorphine-induced locomotor sensitization and conditioned place preference in rats

The locomotor and rewarding effects of the opioid mixed agonist-antagonist buprenorphine were assessed in a conditioned place preference (CPP) experiment. Separate groups of rats were given one of three doses of buprenorphine (0.3, 1.0 or 3.0 mg/kg) or saline paired with the white compartment of a CPP apparatus. The following day, all rats received saline paired with the black compartment. After six conditioning trials, rats were given free access to all compartments of the CPP apparatus. Horizontal activity data obtained during conditioning revealed increased activity (i.e., behavioral sensitization) for the three doses on trial 6. Vertical activity data revealed significant increases on trial 6 for the 1.0 and 3.0 mg/kg doses only. Significant CPP was obtained with the 0.3 mg/kg and 1.0 mg/kg doses of buprenorphine, but not with the 3.0 mg/kg dose. These data indicate that buprenorphine elicits locomotor sensitization after repeated exposures that follows a linear dose-response relationship. In contrast, these data suggest that the rewarding effects of buprenorphine follow an inverted U-shaped dose-response curve.