Adolescent alcohol use may interfere with neurodevelopment, increasing the likelihood of adult
alcohol use disorders (AUDs). We investigated whether adolescent intermittent
ethanol (AIE) exposure alters the adult reward response to
ethanol. Adolescent rats were administered
ethanol once (moderate exposure; Cohort 1) or three times per day (severe exposure; Cohort 2) in a 2 days on/2 days off pattern. In adulthood, subjects responded for electrical stimulation directed at the posterior lateral hypothalamus in a discrete-trial intracranial self-stimulation (ICSS) procedure that provides current-intensity thresholds as a measure of brain reward function. The effects of
ethanol administration and withdrawal were assessed. Control rats showed dose-dependent threshold elevations after acute
ethanol, indicating reward deficits. A majority of moderately AIE-exposed rats (Cohort 1) showed threshold lowering after
ethanol, suggesting
ethanol-induced reward enhancement in this sub-set of rats. Rats exposed to severe AIE (Cohort 2) showed no threshold elevation or lowering, suggesting a blunted affective
ethanol response. Daily
ethanol induced threshold elevations 24h after administration in control rats but not in either group of AIE-exposed rats, suggesting decreased sensitivity to the negative affective state of
ethanol withdrawal. Withdrawal from a 4-day
ethanol binge produced robust and enduring threshold elevations in all rats, although threshold elevations were diminished in rats exposed to severe AIE. These results indicate that AIE exposure diminished reward deficits associated with
ethanol intoxication and withdrawal and may have increased
ethanol-induced reward enhancement in a sub-set of rats. In humans, enhanced
ethanol reward accompanied by reduced withdrawal severity may contribute to the development of AUDs.