Western Michigan University, biological sciences, kalamazoo, MI 49008
GLIAL CELL LINE-DERIVED NEUROTROPHIC FACTOR EXPRESSION IS DIFFERENTIALLY REGULATED BY EXERCISE IN DIAPHRAGM VERSUS PECTORALIS AND EXTENSOR HALLUCIS LONGUS MUSCLE. Monica J. Czarnopys and John M. Spitsbergen*, Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008, john.spitsbergen@wmich.edu.
Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophic factor found in skeletal muscle that affects peripheral motor neurons. Treatment with GDNF promotes survival of motor neurons and rescues them from degeneration. The purpose of our experiment was to examine changes in GDNF protein expression in skeletal muscle from rats that have undergone different durations of exercise. In this study we examined changes in GDNF protein content of rat skeletal muscle in response to involuntary exercise on a running wheel for 2, 4, and 6 weeks. Muscles examined included diaphragm, a respiratory muscle that contracts continuously, and pectoralis (pec) and extensor hallucis longus (ehl) muscles, both of which undergo a substantial increase in contractile activity with exercise. Pectoralis and ehl muscles responded to exercise with an early decrease in GDNF content (2 weeks), followed by a return to control levels after 4 and 6 weeks of exercise. Diaphragm muscle showed a trend towards a steady increase in GDNF content with increasing duration of exercise, with a significant increase being observed following 6 weeks of training. To examine longevity of exercise-induced effects on GDNF expression, we exercised rats for 2 weeks and then allowed 24 hours, 72 hours, or 1 week to pass without exercise, prior to determination of muscle GDNF content. GDNF content of diaphragm was not affected by time after sacrifice; however, both pec and ehl showed a trend towards increased GDNF expression with time after sacrifice, with GDNF content of ehl being significantly increased 72 hours following the last bout of exercise. If GDNF expression in skeletal muscle is regulated by physical activity this could help to explain beneficial effects of exercise on motor nervous system structure and function.
This work was supported by NIH grant 1 R15 AG022908-01A2, The Monroe-Brown Foundation, Western Michigan University, and MSU-KCMS.
[Abstract (DOC)]