Locomotor activity in the hour following dosing in rats given their first or tenth daily dose of methamphetamine (METH, 2.5 mg/kg) or mephedrone (MMC, 30 mg/kg). Error bars represent + S.E.M. On the first day (Figure 2A), the two drug treated groups (MMC×10 and METH×10) travelled greater distance than the three vehicle-treated groups (P<0.01, indicated by ++). On day 10 (Figure 2B) both the combined METH groups and the combined MMC groups travelled greater distance than the VEH group (P<0.01, indicated by *). A logarithmic transformation was applied to the data due to heterogeneity of variance.