Interstrain differences in voluntary binge-like drinking behavior and in two acute ethanol injections-induced synaptic plasticity deficits in rats.

Propensity to drink alcohol and to initiate binge drinking behavior is driven by genetic factors. Recently, we proposed an original animal model useful in the study of voluntary binge-like drinking (BD) in outbred Long-Evans rats by combining intermittent access to 20% ethanol in a two-bottle choice (IA2BC) paradigm to 15-min daily sessions of 20% ethanol operant self-administration. We sought to compare three strains of outbred rats (Long-Evans, Sprague-Dawley, and Wistar) in our BD model. Because we found different propensity to BD between strains, we also sought to test interstrain differences using another procedure of two acute ethanol exposures known to alter long-term depression of hippocampal synaptic plasticity. Our results demonstrate that in both IA2BC and operant procedures, the Long-Evans strain consumed the highest, Wistar the lowest amount of ethanol, and the Sprague-Dawley was intermediate. Long-Evans rats were also the fastest consuming with the shortest time to reach 50% of their maximum consumption in 15 min. When we tested the acute effects of ethanol, long-term depression in hippocampus was abolished specifically in Long-Evans rats with no impact in the two other strains. Thus, our study reveals that the Long-Evans strain is the ideal strain in our recently developed animal model useful in the study of BD. In addition, with the other paradigm of forced acute ethanol exposure, the Long-Evans strain displayed an increase in sensitivity to the deleterious effect of BD on hippocampal synaptic plasticity. Further studies are needed in order to investigate why Long-Evans rats are more prone to BD.