Male C57BL/6J mice were taken from a colony maintained at The University of Texas at Austin (original breeders were purchased from Jackson Laboratories, Bar Harbor, ME). Mice were group-housed 4 or 5 to a cage. Food and water were available ad libitum. The vivarium was maintained on a 12:12 hour light /dark cycle with lights on at 7:00 a.m. The temperature and humidity of the room were kept constant. Baseline drinking began when the mice were 2 to 3 months old. All experiments were conducted in isolated behavioral testing rooms in the Animal Resources Center with reversed light cycle to avoid external distractions. Before beginning experiments, mice were moved to their experimental room and remained there for at least 2 weeks for adaptation to the new light cycle. All experiments were approved by the Institutional Animal Care and Use Committee at The University of Texas at Austin.
