The impact of age of alcohol onset on reward sensitivity

Abstract

The prevalence of alcohol usage disorder (AUD) is rising globally. This is particularly concerning among youths, as adolescent-onset AUD typically predicts worse outcomes compared to adult-onset. However, the adolescent brain’s high adaptability often results in remarkable recovery rates. High reward sensitivity is a risk factor for the development of AUD, making individuals more susceptible to reward-predicting cues. Therefore, we investigated the impact of age on alcohol exposure and reward sensitivity and hypothesized that rats first consuming alcohol during adolescence would show lower reward sensitivity towards reward-predicting cues compared to those first consuming alcohol during adulthood. To test this, rats (n= 88) of postnatal day 42 (adolescent) and postnatal day 77 (adult) were given intermitted alcohol access (IAA) for 2 months using a two-bottle choice paradigm. Rats were divided into high, medium, and low drinkers. High and low drinkers were assessed for the development of incentive salience to a cue, a lever, associated with a free sucrose reward during the Pavlovian Approach Task. Rats could perform either sign-tracking behavior, indicating high incentive value, or goal-tracking behavior, indicating low incentive value. Results show no differences in alcohol consumption between adolescents and adults. Adolescent controls, who consumed no alcohol, showed higher Incentive salience compared to adult control. However, this difference was not found in the alcohol group between the age groups. Adolescent low drinkers exhibited an even lower level of reward sensitivity, suggesting that a low level of alcohol consumption during adolescence can reduce reward sensitivity later in life. It remains unclear whether this difference is caused by low alcohol consumption or is a consequence of low alcohol consumption. This study provides further insight into the differences in drinking behavior between adolescent and adult rats and the associated impact on reward sensitivity, which can help in understanding the development of alcohol addiction.