Housing and Husbandry of ICR Mice

Male and female ICR mice (Envigo, Frederick, MD) were 6–8 weeks old upon arrival to the laboratory, where they were single-housed in cages with corncob bedding (Envigo), a “nestlet” composed of pressed cotton (Ancare, Bellmore, NY), a cardboard tube for enrichment, and ad libitum access to water and food (Teklad LM-485 Mouse/Rat Diet; Envigo). Cages were mounted in racks in temperature-controlled rooms with a 12-h light/dark cycle in a facility approved by the American Association for Accreditation of Laboratory Animal Care. For mice in studies of locomotor activity and gastrointestinal transit, lights were on from 6:00 AM to 6:00 PM, and mice were tested during the light phase of the light/dark cycle. Mice in studies of respiration were housed on a reversed light/dark cycle (lights on from 6:00 PM to 6:00 AM), and tests were conducted during the dark phase of the cycle to reduce the probability of sleep and declining respiratory rates during testing as described previously (36 (link), 37 (link)). All studies began at least 1 week after arrival at the laboratory and were usually completed during the second week after arrival. Animal-use protocols were approved by the Virginia Commonwealth University Institutional Animal Care and Use Committee and complied with the National Research Council Guide for the Care and Use of Laboratory Animals.