Intermittent access to beer promotes binge-like drinking in adolescent but not adult Wistar rats

Teenagers are more likely than adults to engage in binge drinking and could be more vulnerable to long-term brain changes following alcohol abuse. We investigated the possibility of excessive adolescent drinking in a rodent model in which beer (4.44% ethanol vol/vol) is presented to adult and adolescent male Wistar rats. Experiment 1 tracked ad libitum beer and water consumption in group-housed rats from postnatal day (PND) 28-96. Rats consumed an average of 7.8 g/kg/day of ethanol during adolescence (PND 34-55) and this gradually declined to a lower level of intake in adulthood (PND 56-93) of 3.9 g/kg/day. In Experiment 2, beer was made available to both adolescent (PND 29+) and adult (PND 57+) rats for 2h each day in a custom-built "lickometer" apparatus over 75 days. Access to beer was provided either 1 day out of every 3 ("intermittent" groups) or every day ("daily" groups). Relative to body weight, adolescent rats consumed more beer than adult rats in these limited access sessions. Adolescents with intermittent access consumed more than adolescents with daily access, a "binge"-like effect that was not observed in adult groups and that disappeared in adulthood. After 3 months of daily or intermittent alcohol consumption, the preference for beer versus sucrose was assessed. Rats previously kept under an intermittent schedule displayed a higher preference for beer relative to 3% sucrose, but only when testing occurred after 2 days of abstinence. In Experiment 3, adolescent (PND 30-37) and adult (PND 58-65) rats were given 20-min access to beer and their blood alcohol concentrations (BACs) were assessed. Adolescent groups consumed more alcohol than adults and showed higher BACS that were typical of human "binge" drinking (>80 mg/dL). Despite this, the correlation between BAC and beer intake was similar in both age groups. Together these results show that the intermittent presentation of alcohol itself appears to have subtle long-lasting effects on the motivation to consume alcohol. The findings support the use of beer solutions in modeling binge-like patterns of human alcohol consumption in adolescent rats.