Modulation of the behavioral stimulant effects of cocaine after pretreatment with mCPP alone and in combination with SB 242084 in squirrel monkeys (n = 4) trained to lever-press on a fixed-interval 300-s schedule of stimulus termination. A, effects of pretreatment with mCPP (veh, 0.1–0.3 mg/kg) before administration of saline or multiple doses of cocaine. B, effects of pretreatment with SB 242084 (veh, 0.01–0.3 mg/kg) on the mCPP-induced attenuation of behavioral stimulant effects induced by the maximally effective dose of cocaine (coc). Data (mean ± S.E.M.) are expressed as a percentage of responding after administration of the vehicles for all drugs. The dotted lines represent baseline response rate after vehicle treatments (100%). Abscissae, dose of cocaine, relative to EDMax dose determined in each individual subject (A) or dose of SB 242084 (B). Ordinates, normalized response rate.