63.4 Friday, Jan. 6 Aerobic Physiology, Locomotor Behavior, and Glucocorticoids in California Mice DLUGOSZ, E.M.*; HARRIS, B.N.; SALTZMAN, W.; CHAPPELL, M.A.; University of California, Riverside; University of California, Riverside; University of California, Riverside; University of California, Riverside email@example.com
California mice (Peromyscus californicus) have high and variable baseline circulating corticosterone (CORT) levels, which may be important in glucose regulation, energy balance and the stress response. We hypothesized that individual variation in baseline CORT profiles would be correlated with individual differences in energy expenditure (both routine and maximal), aerobic physiology, and activity levels. To investigate this possibility, we tested 54 adult, colony-bred mice for baseline CORT levels (measured near both the circadian peak and the trough), voluntary activity (exercise in running wheels) and its energy costs, maximal oxygen consumption (VO2max), and basal metabolic rate. Given the large number of organismal processes that may be regulated in part by CORT, we found suprisingly few significant relationships between CORT and performance, physiology or morphology, and these differed between the sexes. CORT levels were negatively correlated with both VO2max in females and voluntary distance run in males. Our results, while not striking, suggest that individual CORT profiles may increase our understanding of how the endocrine system integrates and regulates processes at a whole-organism level.