Glucocorticoids, Aerobic Physiology, and Locomotor Behavior in California Mice

Abstract

The glucocorticoid hormones corticosterone (CORT) and cortisol influence numerous physiological, morphological, and behavioral functions. However, few studies have addressed possible relationships between individual differences in glucocorticoid concentrations and whole-animal performance or metabolism. Because CORT is important in glucose regulation and energy metabolism and can influence activity levels, we hypothesized that individual variation in baseline circulating CORT levels would correlate with individual differences in energy expenditure (routine and maximal), aerobic physiology, voluntary exercise on wheels, and organ masses. We tested this hypothesis in the California mouse (Peromyscus californicus). We collected data from 54 adult, colony-bred mice on baseline CORT levels (measured near both the circadian peak and the circadian trough), voluntary wheel running and its energetic costs, maximal oxygen consumption during forced treadmill exercise ([Formula: see text]), basal metabolic rate, and relative organ masses. We found surprisingly few statistically significant relationships among CORT, energy metabolism, behavior, and organ masses, and these relationships appeared to differ between males and females. These findings suggest that individual differences in baseline CORT levels are not an important determinant of voluntary activity levels or aerobic performance in California mice.

Phenotypic differences between the sexes in the sexually plastic mangrove rivulus fish (Kryptolebias marmoratus)

“…maintenance of reproductive tissues) under challenging conditions, and could be explained at the proximate level by sex differences in stress responsiveness. The stress response often results in a dramatic change in metabolic activity, which allows the animal to manage situations that perturb homeostasis (Dlugosz et al, 2012;Martins et al, 2011;Øverli et al, 2005). Although we measured baseline cortisol levels, and found no correlation between baseline cortisol and metabolic rates (i.e.…”

Metabolism at the Max: How Vertebrate Organisms Respond to Physical Activity

“…These methods also have the advantage of allowing the cost of transport to be calculated as the slope of the increase in VO 2 with velocity of movement. More recently, running wheel respirometry has been utilized to determine VO 2max in mammals (42,44,45,67,69). For some ectotherms, achieving VO 2max can result from exploiting behavioral reflexes such as provoking behavioral avoidance using tactile stimulation.…”

The energy cost of voluntary running in weasels,Mustela nivalis

“…Total distances run per day were short, averaging less than 2km, and bouts of running were brief and usually separated by long periods of inactivity (Fig.1). In contrast, many rodents, including deer mice (Peromyscus maniculatus), California mice (P. californicus), laboratory mice (Mus domesticus), goldenmantled ground squirrels (Spermophilus lateralis), least chipmunks (Tamias minimus) and several other species of wild rodents, often run 5-12kmday -1 in the same wheel systems (sometimes more) and running bouts may last for many minutes to hours (Chappell et al, 2004;Rezende et al, 2006;Chappell and Dlugosz, 2009;Dlugosz et al, 2012). The short running distances for weasels are somewhat surprising: carnivores generally have larger home ranges than non-carnivores (e.g.…”

“…Gait-related shifts in power requirements were also lacking in two other mustelids tested in forced running on treadmills: a ferret [Mustela nigripes, 540g (Taylor et al, 1982)] and two fishers [M. pennanti, 3-5kg (Powell, 1979)]. Similarly, no inflections in speed versus power regressions have been reported in rodents tested during voluntary running [deer mice, California mice, laboratory mice, golden-mantled ground squirrels, least chipmunks and Mongolian gerbils (Chappell et al, 2004;Chappell et al, 2007;Rezende et al, 2006;Chappell and Dlugosz, 2009;Dlugosz et al, 2012)]. …”