Impact of Repeated Heavy Ethanol Intoxication During Early Adolescence on Adult Anxiety-Like, Exploratory, Risk Assessment, and Drinking Behaviors in Mice

Drinking beyond binge levels, to the point of passing out, is common among youth and associated with both acute and long-term harm. We evaluated the effects of repeated ethanol-induced heavy intoxication during early adolescence on behavioral outcomes in early adulthood. Male and female C57BL/6J mice (5 weeks old) underwent four Loss of Righting Reflex (LORR) tests over two weeks, induced by intraperitoneal (i.p.) injections of 3.2 g/kg ethanol (intoxicated group) or saline (control group). A subset of intoxicated mice had blood collected on days 1 and 4 for blood ethanol concentration analysis, 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 1.2 g/kg ethanol or saline. In the LDB, adolescent ethanol intoxication led to increased latency to enter the light compartment, although pre-test ethanol did not affect anxiety-like behaviors. Intoxicated females showed enhanced exploratory activity and males had reduced risk assessment behaviors. In the EPM, the effects of pre-test ethanol were more pronounced than adolescence intoxication, producing an anxiolytic effect accompanied by increased exploration and a reduction in risk assessment behaviors. Finally, a separate cohort was tested for ethanol drinking using a two-bottle choice Intermittent Overnight Drinking (IOD) protocol in adulthood. Adolescent ethanol intoxication induced higher ethanol drinking in females. Repeated adolescent intoxication reduced risk assessment while increasing exploratory behavior, indicating riskier decision-making, and selectively elevated ethanol consumption in females.