Dose-response functions for self-administration of cocaine, MDPV, αPVP, MCAT, MDMA, and methylone. Ordinate: injections per session. Abscissa: dose (mg/kg). Filled circles represent points in which self-administration of drug were significantly greater than saline as determined by a Dunnett’s Multiple Comparisons test (cocaine: F4,28=13, p<0.0001; MDPV: F4,44=8.5, p<0.0001; αPVP: F5,40=6.1, p=0.003; MCAT: F6,51=7.2, p<0.0001; MDMA: F4,44=5.5, p=0.0012; methylone: F5,38=5.2, p=0.001) . Error bars represent S.E.M.