Repeated ethanol exposure during early and late adolescence: double dissociation of effects on waiting and choice impulsivity

BACKGROUND: A strong association exists between impulsivity and binge drinking, and between adolescent alcohol exposure and alcohol abuse in humans. To understand the extent to which early-life alcohol exposure contributes to increased impulsivity, we developed an animal model of binge drinking using 2 strains of mice, C57BL/6J (B6) and DBA2/J (D2), that differ in both motor impulsivity and alcohol drinking. METHODS: Mice were treated with 2 g/kg ethanol (EtOH) during their early (intermittent ethanol exposure [IEE]_Early; postnatal day [PND]30 to 45) or late (IEE_Late; PND45 to 60) adolescence or with saline (control group [CON]) throughout the adolescence period. To determine the consequences IEE on waiting impulsivity and attentional function, the number of premature responses and omissions, respectively, were evaluated in adulthood using the 5-choice serial reaction time task (5-CSRTT). To examine the effects of IEE on choice impulsivity, risky decision making was assessed in adulthood using a mouse version of the Iowa Gambling Task (mIGT). Additionally, the acute effects of EtOH in adulthood on waiting impulsivity and choice preference were investigated. RESULTS: We provide experimental evidence that IEE during late, but not early, adolescence disrupts waiting impulsivity and attentional abilities in the 5-CSRTT. In contrast, IEE during early, but not late, adolescence altered risky decision making in the mIGT. D2 mice consistently showed lower premature responding than B6 mice in both the mIGT and the 5-CSRTT, but greater risky decision making on the mIGT. IEE and CON mice showed similar responsiveness to the acute EtOH effects on premature responding, but increased risky choices only in B6_IEE_Early mice. CONCLUSIONS: Our observations suggest a direct effect of IEE during adolescence on waiting and choice impulsivity and attention later in life