Effect of SB-277011A on cocaine self-administration under PR reinforcement. (A,B) Representative records of an individual animal, illustrating the effects of SB-277011A (24 mg/kg, i.p.) on the PR break point for cocaine self-administration. Each short upward mark on the cumulative lever-press records indicates one cocaine infusion. The PR break point was defined as the last completed ratio requirement (lever-presses) for a unit dose of infused cocaine. (C) Mean cocaine dose-dependent self-administration under PR reinforcement, illustrating the cocaine-dose-orderly reduction in PR break point produced by SB-277011A (24 mg/kg, i.p., n = 6 for each cocaine dose group). *P < 0.05, ***P < 0.001, individual group comparison between vehicle and SB-277011A, using the Tukey (a) statistic. (D) Percentage change in PR break point for cocaine self-administration (0.5 mg/kg/infusion) produced by 6, 12 or 24 mg/kg SB-277011A pretreatment on test day compared to PR break point for cocaine self-administration after vehicle pretreatment on test day. *P < 0.05, ***P < 0.001, individual group comparisons using the Tukey (a) statistic, when compared to the vehicle (Veh) pretreatment group.