Abstract: It is becoming increasing apparent that abuse of alcohol during adolescence has long lasting effects of brain and behavior in adulthood. In the present study，we investigated the effect of adolescent alcohol exposure on fear-related behavior in adulthood. Using a rodent model of binge-like adolescent intermittent alcohol （AIE） exposure by vapor inhalation，we observed that exposure to a fear conditioning paradigm of adult rats subjected to AIE leads to alterations in memory consolidation resulting in deficits in fear extinction learning and the recall of extinction memories. However，treatment with an mGluR5 positive allosteric modulator （CDPPB） during fear extinction training attenuated these deficits in extinction learning and retention. In addition，when AIE exposed rats subsequently experienced a single episode of acute stress，we observed a synergistic effect of AIE and acute stress on alterations of fear behaviors. Taken together，these findings suggest that adolescent alcohol abuse may increase vulnerability to development of postsynaptic stress disorders （PTSD） and alcohol use disorders （AUD），and identify potential therapeutic targets for the treatment of these comorbid disorders.