Background: The extensive use of alcohol during adolescence may be facilitated by an age-specific attenuation in sensitivity to adverse effects of ethanol. Adolescent rats are less sensitive than adults to some delayed effects of acute ethanol, including hangover-related anxiety on an elevated plus maze. The purpose of this study was to determine whether adolescent rats are also less sensitive than adults to hangover-related anxiogenesis when indexed in terms of social inhibition.
Methods: Anxiety during ethanol hangover was indexed in adolescent and adult Sprague-Dawley rats of both genders by assessing the suppression in social behavior during a social interaction test. Animals were tested 18 hr after intraperitoneal administration of 0 g/kg (saline) or 4 g/kg ethanol (experiment 1) or at test intervals chosen on the basis of assessments of ethanol clearance time (experiment 2) to equate clearance-to-test intervals across age and gender (experiments 3-5).
Results: Adults showed more hangover-related social suppression and slower postclearance recovery than adolescents. Sex differences were more pronounced in adults than adolescents, with males being more affected than females. Ethanol clearance time was considerably longer in adult males than in adolescent animals and adult females. In contrast to the modest decreases in social activity observed in adolescent animals shortly after ethanol clearance, adolescents showed a surprising increase in play fighting later in the recovery period- a hangover-related social facilitation that was not evident in adults.
Conclusions: The attenuated anxiety and increase in social interactions seen in adolescents during hangover are less likely to serve as deterrents for further drinking than the aversive increase in anxiety seen in adults. A facilitation of social interactions not only during a drinking episode, but also during the postalcohol recovery period, could help to establish a persisting cycle of drinking in at-risk adolescents, leading to dependency and a lifelong history of alcohol-related problems.