Effects of exercise following lateral fluid percussion brain injury in rats

Previous studies have suggested that brain-derived neurotrophic factor (BDN F) is involved in memory and learning, and may be neuroprotective following various brain insults. Exercise has been found to increase BDNF mRNA level s in various brain regions, including specific subpopulations of hippocampa l neurons. In the present study, we were interested in whether following tr aumatic brain injury, exercise could increase BDNF mRNA expression, attenua te neuropathology, and improve cognitive and neuromotor performance. We sub jected adult male Sprague-Dawley rats to a fluid percussion brain injury, f ollowed by either 18 days of treadmill exercise or handling. Spatial memory was evaluated in a Morris Water Maze (MWM) and motor function was evaluate d with a battery of neuromotor tests. Neuropathology was evaluated by measu ring the cortical lesion volume and the extent of neuronal loss in the hipp ocampus, Expression of BDNF mRNA in the hippocampus was assessed with in si tu hybridization and densitometry. Hybridization signal for BDNF mRNA was s ignificantly increased bilaterally in the exercise group in hippocampal reg ions CA1 and CA3 (p < 0.05), but not in the granule cell layer of the denta te gyrus, No significant differences were observed between the groups in ne uropathology, spatial memory, or motor performance. This study suggests tha t after traumatic brain injury, exercise elevates BDNF mRNA in specific reg ions of the hippocampus.