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Glial cell line-derived neurotrophic factor (GDNF) may play a role in delaying

the onset of aging and help compress morbidity by preventing motor unit

degeneration. Exercise has been shown to alter GDNF expression differently in

slow- and fast-twitch myofibers. The aim was to examine the effects of different

intensities (10, 20, ~30, and ~40 m.min-1) of wheel running on GDNF expression

and neuromuscular junction (NMJ) plasticity in slow- and fast-twitch

myofibers. Male Sprague-Dawley Rats (4 weeks old) were divided into two

sedentary control groups (CON4 week, n = 5 and CON6 week, n = 5), two

involuntary running groups, one at a low velocity; 10 m/min (INVOL-low,

n = 5), and one at a higher velocity; 20 m/min (INVOL-high, n = 5), and two

voluntary running groups with resistance (VOL-R, n = 5, 120 g), and without

resistance (VOL-NR, n = 5, 4.5 g). GDNF protein content, determined by

enzyme-linked immunosorbent assay (ELISA), increased significantly in the

recruited muscles. Plantaris (PLA) GDNF protein content increased 174%

(P < 0.05) and 161% (P < 0.05) and end plate-stained area increased 123%

(P < 0.05) and 72% (P < 0.05) following VOL-R, and VOL-NR training,

respectively, when compared to age-matched controls. A relationship exists

between GDNF protein content and end plate area (r = 0.880, P < 0.01,

n = 15). VOL-R training also resulted in more dispersed synapses in the PLA

muscle when compared to age-matched controls (P < 0.05). Higher intensity

exercise (>30 m/min) can increase GDNF protein content in fast-twitch myofibers

as well as induce changes in the NMJ morphology. These findings help

to inform exercise prescription to preserve the integrity of the neuromuscular

system through aging and disease.

Published Citation

Gyorkos, Amy Morrison, and John M. Spitsbergen. "GDNF Content and NMJ Morphology are Altered in Recruited Muscles Following High-Speed and Resistance Wheel Training." Physiological reports 2.2 (2014)

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