Early Ethanol Consumption Predicts Relapse-Like Behavior in Adolescent Male Rats

Background—Alcohol abuse disorders emerge over time with repeated consumption of ethanol, but not all ethanol drinkers develop these disorders. There are pre-existing characteristics that indicate which drinkers are most likely to abuse alcohol. Adolescence, novelty seeking, and high stress reactivity are among the characteristics of the most vulnerable individuals. In addition, an individual’s response to his or her first exposure to the drug influences future consumption. We assessed an array of behavioral and hormonal characteristics in adolescent (28-day-old) male rats before exposure to ethanol, and then determined which rats were most prone to high levels of alcohol drinking. Methods—The assessments consisted of measures of anxiety (elevated plus maze), response to novelty (open field locomotion, novel object exploration), and circulating corticosterone levels after mild restraint and after the elevated plus maze task. After this test battery, the rats were placed in lickometer cages nightly (5 PM to 9 AM) for evaluation of fluid consumption. Rats were first habituated to the cages with water in the lickometer bottles, and then given 10 % (v/v) ethanol for 3 nights as the only available fluid. After this forced ethanol exposure, the rats were allowed t