Alcohol Binge Drinking and Anxiety‐Like Behavior in Socialized Versus Isolated C57BL/6J Mice

Background Binge alcohol drinking has been characterized as a key feature of alcoholism. The drinking‐in‐the‐dark (DID) preclinical model, a procedure that promotes high levels of ethanol (EtOH) intake in short periods of time, has been extensively used to investigate neuropharmacological and genetic determinants of binge‐like EtOH consumption. Using DID methodology, alcohol‐preferring strains of mice such as C57BL/6J (B6) mice consume enough EtOH to achieve blood concentrations (≥1.0 mg/ml) associated with behavioral intoxication (i.e., motor incoordination). DID procedures typically involve the use of socially isolated animals (single‐housed prior to and during the experiment). Previous research indicates that stress associated with social isolation can induce anxiety‐like behavior and promote increases in EtOH intake. The present study investigates the role of housing conditions in anxiety‐like behavior and binge‐like EtOH intake using a DID procedure. Methods Male and female B6 mice were isolated or pair‐housed for a period of 6 weeks prior to evaluation of anxiety‐like (elevated plus maze, light and dark box, open field) and drinking (water, 10% sucrose, 10 to 30% EtOH) behavior. In order to measure intake, a variation of the standard DID procedure using a removable, transparent, and perforated plastic barrier strip (designed to temporarily divide the cage in 2) was introduced. This allowed for individual intake records (2‐hour test) of isolated and socially housed animals. Results Increased anxiety‐like behavior and reduced sucrose consumption were found in isolated mice. The effects of housing conditions on EtOH intake were sex‐ and concentration‐dependent. In male mice, isolation increased 20 and 30% EtOH intake. In females, however, an increased intake of EtOH (30%) was found in socialized animals. No effects of housing or sex were found at EtOH 10%. Conclusions Together with previous literature, the present study suggests that social isolation can promote anxiety‐associated behavior and produce sex‐dependent changes in binge‐like EtOH consumption. The present study highlights the importance of housing conditions in alcohol consumption and anxiety‐like behavior. Using a removable, transparent divider, we tested a modified version of the drinking‐in‐the‐dark model that allowed us to measure 2‐h individual intakes without having to isolate animals (housed in pairs for 22 h per day). Isolation (6 weeks) increased anxiety‐associated behavior and produ