The mouse colony was illuminated during the “dark” phase with a red bulb (2 lumen/square foot, about 21.5 lux). Mice were individually housed in the same type of caging for 5–9 days before testing. During this period, mice were trained to drink from a water spout using a polycarbonate bottle with a stainless steel drinking spout (Ancare Corp., Bellmore, New York). For DID testing, the same type of drinking spout was inserted into 9 mL, calibrated polystyrene tubes for measurement of intake (for details, see Supplement 1). Testing was conducted starting between 50 and 119 days of age with the exception of one family of selected generation 9 (S9) tested at 47 days of age. Details regarding the drinking in the dark phenotype and how it is ascertained have been published (12,13). In addition, a detailed procedural protocol is available at http://www.scripps.edu/cnad/inia/modelmousedrinkingindark.pdf or from the authors on request. Previous studies showed that individual intake values for C57BL/6J mice for DID on the first day of exposure were not highly correlated with DID intakes on Days 2–4 but that intakes on
