The effects of alcohol drinking on subsequent methamphetamine self-administration and relapse in adolescent female rats

Alcohol and Methamphetamine (Meth) are widely abused drugs that are frequently co-abused, though this pattern of polysubstance abuse is rarely studied. Alcohol use during adolescence is associated with subsequent Meth dependence in humans and female adolescents may be more vulnerable than males to serial alcohol and Meth use. However, it is unknown if prior alcohol drinking impacts subsequent Meth-taking in female rats. This study uses a novel method of serial voluntary alcohol drinking and Meth self-administration in female adolescent Sprague Dawley rats (n = 35) to model human patterns of co-abuse. Rats demonstrated a steady time-based increase in alcohol preference versus water, starting at 33.3 +/- 3.4% on day 1-48.0 +/- 3.6% by the final day of EtOH, with a peak EtOH preference of 49.7 +/- 3.7% on day 17 of the drinking paradigm (P < 0.001, one-way repeated measures ANOVA). All rats rapidly acquired Meth self-administration, demonstrating a 4.6 +/- 1.4 fold increase in active presses for Meth and a 5.2 +/- 1.8 fold increase in Meth intake (mg/kg) within 7 days, and maintained high levels of Meth intake throughout 21 days of self-administration. Prior alcohol drinking did not alter the increase in Meth self-administration compared to alcohol naive control rats. However, after 7 days of Meth abstinence, a history of alcohol drinking reduced cue-primed reinstatement of Meth seeking. These findings demonstrate that prior alcohol consumption does not alter overall Meth self-administration but does persistently reduce cue-primed Meth seeking after prolonged alcohol abstinence.