Effects of treadmill exercise on spatial learning, memory and expression of hippocampal brain-derived neurotrophic factor of rats after mild traumatic brain injury

Objective To investigate the effects of treadmill exercise on spatial learning,memory and the expression of hippocampal brain-derived neurotrophic factor(BDNF) in rats after mild traumatic brain injury (TBI).Methods Thirty Sprague-Dawley rats were randomly divided into group T (n =10,undergoing TBI modelling operation and 4 weeks' treadmill exercise training beginning at 48 h after the operation),group C (n =10,undergoing TBI modelling operation and no exercise training) and group N (n =10,undergoing sham operation and no exercise training).Morris water maze(MWM)was used to test rats' abilities of spatial learning and memory.The number of BDNF-positive cells in the hippocampus was measured with immunohistochemistry.Results In the orientational navigation test,the escape latency period was gradually shortened for rats in all groups.At the second training week,the average time of group T(88.54 ±5.73 s) became shorter than that in group C (91.45 ± 8.91 s).At the fourth week,however,the difference [(55.33 ± 6.77 s) vs (74.53 ± 6.85 s)] was significant(P ＜ 0.01).Group N (88.44 ±7.79 s,79.52 ± 8.02 s,69.54 ± 10.14 s and 62.49 ± 7.22 s respectively) also improved significantly more than group C (98.99 ± 6.84 s,91.45 ± 8.91 s,79.65 ± 12.47 s and 74.53 ± 6.85 s respectively) from week 1 to 4 (P ＜ 0.01).The average number of times of passing through the platform area of group N in four weeks (3.00 ± 0.54,3.38 ± 0.74,4.38 ± 1.06 and 6.00 ± 0.76 respectively) and group T from the second week on(3.25 ± 1.28,5.00 ± 0.93 and 5.88 ± 0.99 respectively) were significantly higher than that of group C (1.25 ± 0.71,1.50 ± 0.54,2.13 ± 1.25 and 3.00 ± 0.54 respectively) accordingly (P ＜ 0.01).At the week four,the average number of BDNF-positive cells in group T(128.56 ± 7.93) were significantly larger than that in group C and group N (P ＜ 0.05),with no significant difference was noted between group N and group C (P ＞0.05).Conclusions Treadmill exercise could improve the spatial learning and memory of rats after mild traumatic brain injury.This may be related with the up-regulation of expression of BDNF in the hippocampus. Key words: Treadmill exercise;  Traumatic brain injury;  Learning and memory;  Brain-derived neurotrophic factor