Animals

C57BL/6J (B6) male mice were used in all experiments. Original breeders were purchased from Jackson Laboratories (Bar Harbor, ME) and a colony has been maintained at The University of Texas at Austin. Mice were initially group-housed 4–5 to a cage. Before ethanol-drinking experiments, animals were moved to the experimental room and remained there for at least 2 weeks to adapt to a reversed 12:12-hour light:dark cycle (lights off at 10:00 AM). When animals were approximately 60 days old, they were individually housed and ethanol-drinking procedures were begun. Food was available ad libitum. The temperature and humidity of the rooms were kept constant. Experiments were approved by the Institutional Animal Care and Use Committee at The University of Texas at Austin.