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Glial cell line-derived neurotrophic factor (GDNF) is considered to be one of the most potent neurotrophic factors for motor neurons of the spinal cord. However, little is known about the response of GDNF in the spinal cord following exercise from healthy individuals.PURPOSE:Previous studies from our laboratory have shown that long term voluntary exercise (6 weeks and 6 months) has no effect on GDNF protein content in rat spinal cord. Therefore, the aim of the current study was to examine changes in GDNF protein content in the spinal cord following 2 weeks of voluntary exercise from adult and aged rats.METHODS: Male Sprague Dawley rats aged 6 months and 2 years were examined. The exercised animals were housed with continuous access to voluntary running wheels for 2 weeks. Age-matched sedentary control animals had no exposure to the voluntary wheels. GDNF protein content of the spinal cord was measured using an enzyme-linked immunosorbent assay (ELISA) and western blot analysis. Immunohistochemical analysis was performed to localize GDNF in nerve cells in the spinal cord. RESULTS: The 6-month-old animals that had undergone 2 weeks of voluntary exercise ran an average distance of 25,828.7 m whereas the 2-year-old animals ran an average distance of 1683.2 m. Total GDNF protein content in the spinal cord of 6 month old animals was significantly decreased following 2 weeks of voluntary exercise (1293.4 188.9 pg GDNF) as compared to sedentary control animals (2298.6 374.5 pg GDNF). Two weeks of voluntary exercise for the spinal cord of the 2 year old animals was approaching significant increase of total GDNF (p = 0.08) when compared to age-matched sedentary control animals (1797.8 370.1 pg GDNF and 792.0 222.2 pg GDNF, respectively). CONCLUSION: Short term voluntary exercise may increase GDNF protein content in the spinal cord of aged individuals and may act as a measure to prevent motor neuron loss commonly associated with senescence.

This work was supported by a grant from the Faculty Research and CrativeActivities Award, Western Michigan University, NIH grant 1 R15 AG022908-01A2, NSF grant DBI 0552517 and MSU-KCMS.

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