Subjects
The sixteen, 8–10 week old, 25–30 g mice (8 per genotype) used in this study were the congenic offspring of breeders that were descendants of the original F2 hybrid (129/Sv × C57BL/6J; Kelly et al., 1997) that was backcrossed to inbred C57Bl/6J stock (Jackson Laboratories, ME). This breeding strategy was repeated for 20 successive generations with the gender of the donor/mutant alternating with each generation. All experimental subjects were genotyped by PCR as previously described [23]. All testing occured randomly across estrous cycles. The Department of Comparative Medicine at Oregon Health and Science University approved all protocols, and all animals were maintained in accordance to National Institutes of Health's Guide for the Care and Use of Laboratory Animals.