(a) Active lever responses during conditioning sessions in the presence of stimuli paired with COC (reward + S+) vs. non-availability of COC (non-reward + S−) or active lever responses during conditioning sessions in the presence of stimuli paired with SCM (reward + S+) vs. non-availability of SCM (non- reward + S−). ***p < 0.001, vs. non-reward + S−. (b) Following extinction (EXT), presentation of the COC S+ or SCM S+ elicited strong recovery of responding in vehicle-treated rats (0 mg/kg, ##p < 0.01, vs. EXT and S−) and modification of conditioned reinstatement across doses of SB334867 (***p < 0.001, vs. 0 mg/kg; +p < 0.05, ++p < 0.01, vs. EXT and S−).