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. Author manuscript; available in PMC: 2015 Aug 1.
Published in final edited form as: Drug Alcohol Depend. 2014 May 28;141:92–98. doi: 10.1016/j.drugalcdep.2014.05.010

Figure 1.

Figure 1

Panel A: The percentage of PN and PS animals reaching criterion for stable METH self-administration during FR-1 and FR-3 training. Panel B: The percentage of male and female animals reaching criterion for stable METH self-administration during FR-1 and FR-3 training. On days 2, 3, and 4 of FR-3 training, females acquired responding significantly faster than males, * = p < 0.05. Stable criterion was defined as less than 20% variability in active lever responding across two consecutive sessions; greater than 2:1 ratio of active to inactive responses, and a minimum of 10 infusions per session.