Submitted on June 30, 2007
Accepted on October 1, 2007
Short-term treadmill running in the rat: what kind of stressor is it?
David A. Brown1, Micah S. Johnson1, Casey J. Armstrong2, Joshua M. Lynch1, Nicholas M. Caruso1, Lindsay B. Ehlers1, Monika Fleshner1, Robert L. Spencer3, and Russell L. Moore1*
1 Integrative Physiology, University of Colorado at Boulder, Boulder, Colorado, United States
2 Boulder, Colorado, United States; Integrative Physiology, University of Colorado at Boulder, Boulder, Colorado, United States
3 Psychology, University of Colorado at Boulder, Boulder, Colorado, United States
* To whom correspondence should be addressed. E-mail: Rmoore{at}colorado.edu.
The use of short-term (1 to 5 days) treadmill running is becoming increasingly common as a model to study physiological adaptations following exercise. Although the benefits of acute exercise seem clear, a paucity of data exist describing potential markers of stress in response to forced running. We subjected male and female Sprague-Dawley rats to 0 to 10 days of treadmill running. Twenty-four to thirty-two hours after the last bout of exercise animals were sacrificed and examined for training-induced changes in several physiological variables. No effect of skeletal citrate synthase activity was observed in the male animals, and only at 10 days of running did females show a significant increase in citrate synthase. Myocardial heat shock protein 72 (HSP72) content was higher in male than female rats, and exercise increased HSP72 in both sexes, although the time-course was different between sexes. Animals displayed several markers of stress in response to the treadmill running, and in a sex-dependent manner. Serum corticosterone was significantly elevated in both sexes 24 hours after exercise in three of four exercise groups. Corticosterone binding globulin was higher in females, and decreased after running in female rats. Body and spleen weights decreased in males (but not females) in response to the exercise training, and running did not alter adrenal gland weights in either sex. These data indicate that in response to short-term treadmill running both male and female rats show signs of systemic stress, and the pattern of changes occurs in a sex-specific manner.
