Treadmill running protects spinal cord contusion from secondary degeneration

It is known that physical activity triggers changes in the central nervous system. Adult rats, trained on treadmills for 4 weeks, and a group of sedentary rats was submitted to contuse moderate spinal cord injury. A group of sedentary rats was submitted to a sham operation. The trained group continued running on treadmill after lesion for 4 weeks. Motor behavior evaluated by BBB score was smaller in the sedentary group compared to the trained rats by 7 days after lesion. Computerized activity monitor showed clear-cut differences in spontaneous motor parameters in trained rats only before lesion. After surgery, sedentary rats showed changes in motor parameters but not in later periods of analysis. Animals were euthanized by 28 days after surgery, and their spinal cords were processed for Nissl staining and immunohistochemistry. The number of the remaining neurons and the lesion areal and lesion volume fractions were obtained by stereological method. The number of the remaining neurons did not change after training. Lesion volume and lesion areal fraction per section were smaller in the trained group. Lesion index was more pronounced in the sedentary group. Microdensitometric image analysis demonstrated a microglial reaction, astroglial activation, and glial FGF-2 production more pronounced in the spinal cord of sedentary animals. GAP-43 was higher in caudal levels of contusion in the sedentary group. In conclusion, treadmill running may favor a better functional recovery in the acute period after spinal cord lesion and wound repair processes leading to neuroprotection.