Acquisition and maintenance of methamphetamine self-administration. Illustrated is methamphetamine (meth) self-administered as 0.1 mg/kg/0.1 ml on a fixed ratio (FR) 5 schedule of reinforcement. Forty rats completed the paradigm and were tested for cue reactivity (CR). (A) Protocol days 8–14; rats demonstrated stable self-administration. As measured by one-way rmANOVA, no significant differences occurred across the last 3 days of self-administration (days 12–14) for active lever presses (F(3,37) = 8.95; two statistical outliers removed), inactive lever presses (F(3,35) = 4.94; four statistical outliers removed), or infusions (F(3,37) = 12.46; two statistical outliers removed). (B) Protocol days 16 and 26. Between each cue reactivity (CR) assessment, rats were allowed to self-administer for two consecutive days on an FR5 schedule for 3 hr/day. Using paired t-tests, no differences occurred between days 16 and 26 for active lever pressing (p = 0.89; one statistical outlier removed), inactive lever pressing (p = 0.23; three statistical outliers removed) or number of infusions received (p = 0.76; one statistical outlier removed).
Graves and Napier BMC Neuroscience 2012 13:65 doi:10.1186/1471-2202-13-65