Consequences of Adolescent or Adult Ethanol Exposure on Tone and Context Fear Retention: Effects of an Acute Ethanol Challenge During Conditioning

BackgroundAn acute ethanol (EtOH) challenge prior to fear conditioning typically disrupts fear retention to contextual cues to a greater degree than fear retention to a discrete tone cue, and adolescent rats are less sensitive than adults to these EtOH-induced disruptions of context fear memory. Given that some research suggests that repeated EtOH exposure during adolescence may lock-in adolescent-typical EtOH sensitivity into adulthood, the purpose of this study was to determine whether adults exposed to EtOH as adolescents would be less sensitive to EtOH-induced disruptions of context fear. MethodsMale Sprague-Dawley rats were given 4g/kg intragastric EtOH (25% v/v) or water every 48hours for a total of 11 exposures during adolescence (postnatal day [P] 28 to 48) or adulthood (P70-90). After a 22-day non-EtOH period, animals were acutely challenged with 1g/kg intraperitoneal EtOH or saline 10minutes prior to tone or context (noncued) fear conditioning. Tone and context fear retention was subsequently examined. ResultsRegardless of age or exposure history, typical deficits in context fear retention were evident after EtOH challenge during conditioning. Similarly, tone fear retention was disrupted in all animals that were trained in the presence of EtOH, which was somewhat surprising given the relative resistance of tone fear retention to an acute EtOH challenge. ConclusionsThese results do not support the notion of a lock-in of adolescent-typical EtOH sensitivity as there was no influence of exposure age on sensitivity to the disruptive effects of an acute EtOH challenge. Thus, it appears that not all adolescent-like EtOH sensitivities persist into adulthood after prior EtOH exposure during adolescence.