Sex Differences in Neurotrophin Expression After Treadmill Training Following Peripheral Nerve Injury
By Hohsuan Tiffany Jang
Modest daily treadmill training applied following traumatic injury to peripheral nerves results in an enhancement of subsequent axon regeneration. This enhancement is found only in males. Since an increase in brain derived neurotrophic factor (BDNF), neurotrophin 4/5 (NT-4/5), and their common receptor, trkB, in spinal motoneurons has been proposed to underlie this enhancement, the purpose of this study was to evaluate the sex-dependence of treadmill training in inducing the expression of these molecules in axotomized motoneurons. After cutting their sciatic nerves, male and female mice were treadmill trained for one hour daily for two weeks. Histological sections through the L3-L5 regions of the lumbar spinal cords of euthanized mice were processed for the demonstration of BDNF or NT-4/5 mRNA using fluorescent in situ hybridization, or for trkB receptors using immunohistochemistry. Overall BDNF mRNA, NT-4/5 mRNA, and trkB expression was determined by measuring motoneuron mean fluorescence intensity, soma size, and the number of positively labeled motoneurons. Mean fluorescence intensity and soma size of lamina IX motoneurons were determined for both sexes after BDNF mRNA, NT-4/5 mRNA, and trkB assays were performed. Additionally, the mean number of BDNF mRNA, NT-4/5 mRNA, and trkB-expressing motoneurons per spinal cord section was determined for each sex. Males were found to express significantly more BDNF mRNA, NT-4/5 mRNA, and trkB by the recruitment of more BDNF mRNA, NT-4/5 mRNA, and trkB-expressing motoneurons than females. Furthermore, in males, motoneurons from the side of the spinal cord associated with the nerve transection had greater expression of BDNF mRNA at the level of the individual motoneuron.
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About this Honors Thesis
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|Sex Differences in Neurotrophin Expression After Treadmill Training Following Peripheral Nerve Injury ()||2018-08-28||