Figure 2: (a) Total number of infusions obtained during the first 21 days of 2 hr daily access sessions for each dose of methylone tested (n=12 for 0.05 and 0.5 mg/kg/infusion groups; n = 11 for the 0.1 and 0.2 mg/kg/infusion groups). (b) Percent of animals at or above criterion (10 active lever presses per session) for each experimental session.