Effects Of Treadmill Exercise On Spatial Learning And Memory Abilities And Expression Of Hippocampal BDNF In Rats After Mild Traumatic Brain Injury

Cognitive impairments is prevalent clinical manifestation of traumatic braininjury(TBI).Evidence have shown that cognitive disorder was frequently related toimpaired hippocampal function, unfortunately there is still no scientificallyestablished effective interventions. Based on evidence that voluntary exercise canup-regulate the expression of brain derived neurotrophic factor(BDNF) withinhippocampus of healthy rats and this exercise-induced increase in BDNF has beensuggested as one of the main mechanisms for the effects of exercise on cognition.However, there is few research focusing on the correlation betweenconstraint-induced voluntary exercise-induced increase of BDNF within hippocampusand amelioration in cognition after TBI. Therefore, the present study was designed toobserve the influence of treadmill, one of training method in constraint-inducedvoluntary exercise, on the special learning and memory abilities of rats after mild TBIand discuss the relationship between treadmill exercise and the expression of BDNFin hippocampus. ObjectiveTo investigate the effects of treadmill exercise on spatial learning and memoryabilities and expression of hippocampal BDNF in Sprague-Dawley rats after mildtraumatic brain injury.MethodsA total of36eligible male Sprague-Dawley rats were utilized in this experimentand were randomly divided into3groups, which consist of T group (n=12,operationand exercise training), C group (n=12,operation and non-exercise training) and Ngroup (n=12, sham-operated and non-exercise training). Rats were subjected tosurgery and the freely falling object was used to stimulate either TBI models(T groupand C group) or sham(N group). At the3rddays post injury, rats in T group receivedtreadmill exercise based on exercise program while rats in C group and N group werehoused on static treadmill. Rats were trained in the Morris Water Maze to test theirabilities of learning and memory at7days,14days,21days and28days aftertreadmill exercise respectively. The gray value and number of positive cells of BDNFwithin hippocampal CA1cell stained by immunohistochemistry(ICH) was mesruedby Image-Pro Plus6.0.ResultsAcross all groups of rats there were no significant differences in swim-speed,indicating that at30days after TBI rats did not exert general swimming deficit.Both TBI and treadmill exercise influenced the performance of rats in T group.Asignificant group effect was found for escape latent period in place navigation test at28days after exercise(F=15.59, p<0.001) and for spatial probe test(F=37.58,p<0.001).As compared with that in rats in C group and N group, significant decreaseof escape latent period was noted in rats of T group in place navigation test(P<0.01),while no significant difference of that was noted between N group and Cgroup(P>0.05). The times passing through the platform area were counted in thespatial probe test(the platform was removed),significant difference was noted betweeneach two groups(P<0.01). These improvements exhibited in MWM indicated that treadmill exercise can enhance the special learning and memory abilities in rats aftermild TBI.The gray value of BDNF within hippocampal CA1cell in T group was lower thanthose in C group(p<0.05) and N group(p<0.05),indicating that treadmill exercise canup-regulate the expression of BDNF within hippocampus.ConclusionTreadmill exercise could improve the special learning and memory abilities andenhance the expression of hippocampal BDNF of rats after mild traumatic brain injury.So we can infer that the improvement of learning and memory abilities may be relatedwith the increasement of hippocampal BDNF.