Effect of SB334867 Orx-A/Hcrt-1’s priming effect. (A) Time course of cocaine self-administration over the 21 days of training. Tukey post hoc tests *P < 0.05; **P < 0.01; ***P < 0.001 vs. respective previous day (data shown depict the mean ± S.E.M; n = 38). (B) Lack of effect of SB334867 on Orx-A/Hcrt-1 (0.5 µg) priming effect: *P < 0.05, vs. VEH (DMSO): ∆: % decrease in responding: *P < 0.05, vs. VEH (DMSO). Asterisks (*) refer to both the responses and the % decrease. EXT, extinction; SHAM, sham injection; VEH, vehicle (data shown depict the mean ± S.E.M; n = 38 for EXT and SHAM; n = 9 for VEH; n = 7–9 for SB334867 doses).