Binge pattern ethanol exposure in adolescent and adult rats: Differential impact on subsequent responsiveness to ethanol

Background: Recent evidence indicates that adolescent animals are more sens itive than adults to the disruptive effects of acute ethanol exposure on sp atial learning. It is not yet known whether adolescent animals are also mor e sensitive than adults to the enduring neurobehavioral effects of repeated ethanol exposure. In this study, animals were exposed to ethanol in a bing e-pattern during either adolescence or adulthood. At a time when all subjec ts were adults, spatial working memory was examined in the absence and pres ence of an acute ethanol challenge. Methods: Rats were exposed to ethanol (5.0 g/kg intraperitoneally) or isovo lumetric saline at 48 hr intervals over 20 days. Exposure began on either p ostnatal day 30 (adolescent group) or 70 (adult group). Twenty days after t he final injection, a time at which all animals were adults, the subjects w ere tested on an elevated plus maze and then were trained to perform a spat ial working memory task on an eight-arm radial maze. At the beginning of ea ch session of training on the working memory task, subjects retrieved food rewards on four of the eight arms. After a delay, subjects were placed on t he maze and allowed to retrieve food from the remaining four arms. Results: Prior exposure to ethanol did not influence behavior on the plus m aze. Performance of the groups did not differ during acquisition of the spa tial working memory task with a 5 min delay or during subsequent testing wi th a 1 hr delay. However, animals treated with ethanol during adolescence e xhibited larger working memory impairments during an ethanol challenge (1.5 g/kg intraperitoneally) than subjects in the other three groups. Conclusions: The findings indicate that binge pattern exposure to ethanol d uring adolescence enhances responsiveness to the memory-impairing effects o f ethanol in adulthood.