Drinking in the dark (DID)

The DID test is a mouse model of binge drinking that results in pharmacologically relevant blood alcohol levels (BALs) (⩾80 mg%).²³ Each mouse was provided with a modified sipper tube in the home cage that contained either 20% ethanol (Decon Labs, King of Prussia, PA, USA) in water or water (for the control group), 3 hours into the dark cycle.²⁴ Mice were acclimated to the sipper tube containing water for one 2 hours drinking session on Friday, 3 days prior to providing them with ethanol or water in the DID procedure. Mice were weighed 4 hours before the start of the DID test. Mice were given 2 hours access to the 20% ethanol solution or water from Monday to Wednesday, 3 hours into the dark cycle, and the amount of fluid consumed was measured at the end of each drinking session. On the fourth day (Thursday), mice had access to the ethanol or water for 4 hours and the amount of fluid consumed was measured at both 2 and 4 hours. For mice that underwent repeated cycles of drinking in the dark (ie, lentiviral experiments), ethanol bottles were replaced with standard water bottles on Thursday after the drinking session and DID was resumed on the following Monday (3 days off, followed by 4 days on ethanol). These same mice were also tested for sucrose consumption 3 days after the completion of the ethanol drinking test and were provided with 2% (w/v) sucrose solution using the same procedures as the ethanol test and were euthanized 1 day (~20 hours) following the completion of the fourth sucrose drinking test.