Binge drinking (BD) is often defined as a large amount of alcohol consumed in a 'short' period of time or 'per occasion'. In clinical research, few researchers have included the notion of 'speed of drinking' in the definition of BD. Here, we aimed to describe a novel pre-clinical model based on voluntary operant BD, which included both the quantity of alcohol and the rapidity of consumption. In adult Long-Evans male rats, we induced BD by regularly decreasing the duration of ethanol self-administration from 1-hour to 15-minute sessions. We compared the behavioral consequences of BD with the behaviors of rats subjected to moderate drinking or heavy drinking (HD). We found that, despite high ethanol consumption levels (1.2 g/kg/15 minutes), the total amounts consumed were insufficient to differentiate HD from BD. However, consumption speed could distinguish between these groups. The motivation to consume was higher in BD than in HD rats. After BD, we observed alterations in locomotor coordination in rats that consumed greater than 0.8 g/kg, which was rarely observed in HD rats. Finally, chronic BD led to worse performance in a decision-making task, and as expected, we observed a lower stimulated dopaminergic release within nucleus accumbens slices in poor decision makers. Our BD model exhibited good face validity and can now provide animals voluntarily consuming very rapidly enough alcohol to achieve intoxication levels and thus allowing the study of the complex interaction between individual and environmental factors underlying BD behavior.

For several decades, studies conducted to evaluate the efficacy of RS(±)‐Baclofen in the treatment of alcohol dependence yielded contrasting results. Human and animal studies recently questioned the use of the racemic drug in patients since a potential important role of the different enantiomers has been revealed with an efficacy thought to reside with the active R(+)‐enantiomer. Here we conducted experiments in the postdependent rat model of alcohol dependence to compare the efficacy of R(+)‐Baclofen or S(−)‐Baclofen to that of RS(±)‐Baclofen on ethanol intake, seeking, and relapse. R(+)‐Baclofen was more effective than RS(±)‐Baclofen in reducing ethanol intake and seeking during acute withdrawal and during relapse after abstinence. We also used an original population approach in order to identify drug responders. We found a significant proportion of responders to S(−)‐Baclofen and RS(±)‐Baclofen, displaying an increase in ethanol intake, and this increasing effect on alcohol intake was not seen in the R(+)‐Baclofen group. At an intermediate dose of R(+)‐Baclofen, devoid of any motor side effects, we identified a very large proportion of responders (75%) with a large decrease in ethanol intake (90% decrease). Finally, the response to RS(±)‐Baclofen on ethanol intake was correlated to plasma level of Baclofen. R(+)‐Baclofen and RS(±)‐Baclofen were effective in reducing sucrose intake. Our study has important clinical implication since it suggests that the wide variability in the therapeutic responses of patients to RS(±)‐Baclofen may come from the sensitivity to the R(+)‐Baclofen but also to the one of the S(−)‐Baclofen that can promote an increase in ethanol intake.

Binge drinking (BD) is a harmful behavior for health and is a predictive factor for the development of alcohol addiction. Weak decision-making (DM) capacities could play a role in the vulnerability to BD which in turn would lead to DM impairments, thus perpetuating BD. Longitudinal preclinical studies are however lacking and necessary to understand this complex relationship. Both DM and BD are influenced by sex and involve dopamine release in the core of the nucleus accumbens, a central mechanism regulated by dopamine D2/3 autoreceptors. In this context, we used an operant self-administration procedure of BD in male and female rats, and longitudinally assessed DM capacity, memory and anxiety-like behavior. To better understand the mechanisms potentially involved in the relationship between DM and BD, ex vivo dopamine transmission was assessed short term after the end of the binge exposure in the core of the nucleus accumbens (NAc) using the fast-scan cyclic voltammetry (FSCV) technique and the D2/3 agonist quinpirole. We found important basal sex differences in DM, with female rats showing better performances at baseline. Choice processes were impaired exclusively in males after BD history, associated with a decrease in impulse control in both sexes, while memory and anxiety-like behavior were not affected. Our neurobiological results demonstrate that BD did not affect basal dopamine signaling in the NAc core, regardless of the sex, but reveal changes in the sensitivity to the inhibitory effects of quinpirole in females. DM impairments were neither associated with changes in basal dopamine signaling nor pre-synaptic D2 activity. Overall, our findings show that BD affects both DM processes and dopamine transmission in the core of the NAc in a sex-related manner, further suggesting that these effects may play a role in the vicious cycle leading to BD perpetuation and the early onset of AUD. Our results may inform novel strategies for therapeutic and prevention interventions.