Regional changes in concentrations of brain norepinephrine [NE] and its metabolites after chronic exercise have not been described for exercise protocols not confounded by other stressors. We examined levels of [NE], 3-methoxy-4-hydroxyphenylglycol [MHPG], and 3,4-dihydroxyphenylglycol [DHPG] in the frontal cortex, hippocampus, pons-medulla, and spinal cord after 8 wk of exercise. Male Sprague-Dawley rats (N = 36) were randomly assigned to three conditions: 1) 24-h access to activity wheel running (WR), 2) treadmill running (TR) at 0° incline for 1 h·d-1 at 25-30 m·min-1, or 3) a sedentary control group (C). Levels(nmol·g-1) of [NE], [MHPG], and [DHPG] were assayed by high performance liquid chromatography with electrochemical detection. Planned contrasts (P < 0.05) indicated that exercise training increased succinate dehydrogenase activity (mmol cytochrome C reduced·min-1·g-1 wet weight) in soleus muscle for TR compared with WR or C. [NE] was higher in the pons-medulla and spinal cord for both TR and WR compared with C. [DHPG] was higher in the pons-medulla for TR compared with C, and [MHPG] was higher in the frontal cortex and in the hippocampus for TR compared with C. Our results suggest that treadmill exercise training is accompanied by brain noradrenergic adaptations consistent with increased metabolism of NE in areas containing NE cell bodies and ascending terminals, whereas treadmill running and wheel running are accompanied by increases in levels of NE in the areas of NE cell bodies and the spinal cord, independently of an exercise training effect.
Departments of Exercise Science and Pharmacology, The University of Georgia, Athens, GA 30602-3654
Submitted for publication January 1993.
Accepted for publication November 1995.
This research represents part of A. L. Dunn's dissertation directed by R. K. Dishman.
Current addresses for: Robert B. Armstong, Ph.D., Department of Health and Kinesiology, Texas A&M University, College Station, TX 77845; Efirstname.lastname@example.org; Shawn D. Youngstedt, Ph.D., Department of Psychiatry, Circadian Pacemaker Laboratory, The University of California, San Diego, CA 92093-0667; E-mail email@example.com.
Address for correspondence: Rod K. Dishman, Ph.D., Department of Exercise Science, The University of Georgia, 300 River Road, Athens, GA 30602-3654; E-mail: firstname.lastname@example.org or Andrea L. Dunn, Ph.D., Division of Epidemiology, The Cooper Institute for Aerobics Research, Dallas, TX 75230; E-mail:email@example.com.