Fig. 2.

Acquisition and escalation of METH (0.1 mg/kg/infusion) intravenous self-administration during short access (ShA: 2 h/day) and long access (LgA: 6 h/day) in male and female rats. a Active and Inactive lever presses. b METH infusions (0.1 mg/kg) and total intake. Inset graph illustrates the difference in total METH intake between ShA and LgA rats. c Locomotor activity. d Development of binge-like METH intake in LgA trained rats (combined male and female), comparing the first and final 2 and 6 h sessions in 15-minute bins. Inset graph illustrates the comparison between the first 2 h of the labelled sessions in LgA rats. ^#p < 0.05. *p < 0.05 from 6 h D1. Data are presented as mean ± SEM. n = 16/sex/group.