Repeated early-adolescent ethanol intoxication promotes riskier decision-making in adult male mice and increases drinking in adult female mice

Exceeding binge-level alcohol drinking is common among adolescents and is associated with both short- and long-term adverse outcomes. This study evaluated the effects of repeated ethanol intoxication during early-adolescence on behavioral outcomes in early-adulthood. Male and female C57BL/6 mice (5 weeks old) received four intraperitoneal (i.p.) injections, over two weeks, of either saline (control) or 3.2 g/kg ethanol (intoxicated). A subset of intoxicated mice had blood collected on days 1 and 4, confirming heavy intoxication (∼289 mg/dL). At 9 weeks of age, animals were tested in the Light-Dark Box (LDB) and Elevated Plus Maze (EPM) immediately after receiving either saline or 1.2 g/kg ethanol (i.p.). In the LDB, ethanol intoxication in early-adolescence did not affect anxiety-like behaviors but reduced risk assessment in males, indicating riskier decision-making.In the EPM, pretest ethanol produced an anxiolytic effect, accompanied by increased exploration and a reduction in risk-assessment behaviors, while intoxication during adolescence did not yield significant effects. To better characterize behavioral organization beyond discrete measures, we applied Markov chain models to quantify first-order transition probabilities to and from risk-assessment behaviors. This analysis revealed that pretest ethanol markedly reduced the complexity of behavioral structure, especially in the EPM. Finally, a separate cohort of control and intoxicated mice underwent a two-bottle choice Intermittent Overnight Drinking protocol in adulthood. Ethanol intoxication in early-adolescence increased voluntary ethanol intake in adult females but not in males. These findings highlight long-lasting and sex-specific consequences of early-adolescent intoxication on risk-related behaviors and alcohol consumption.