外源性脑源性神经营养因子对Alzheimer大鼠行为学的影响及其作用机制

摘要

目的 观察外源性脑源性神经营养因子(BDNF)对Alzheimer大鼠脑内突触素表达的影响及对大鼠行为学的作用,探讨其可能的作用机制.方法 健康成年雄性Wistar大鼠60只,随机平均分为正常对照组、假手术组、冈田酸(OA)组、BDNF组、K252a组和LY294002组.按照大鼠脑立体定位图谱定位,于海马CA3区注射点,在每侧海马假手术组大鼠注射2μL生理盐水,OA组注射2μLOA (0.2 μmol/L),BDNF组注射2μL OA+2 μL BDNF (50 ng/mL),K252a组注射2 μL OA+2μLBDNF+2μL K252a(4 μmol/L),LY294002组注射2μL OA+2μL BDNF+2 μL LY294002(4μmol/L).通过水迷宫试验检测大鼠行为学改变,通过Western blot检测大鼠脑内突触素、pThr231的表达.结果 定向航行实验显示,OA组及K252a组大鼠逃避潜伏期较正常对照组、假手术组、LY294002组及BDNF组明显延长(P＜0.01),BDNF组及LY294002组大鼠逃避潜伏期较正常对照组及假手术组也明显延长(P＜0.01),正常对照组与假手术组比较无统计学差异(P＞0.05).空间探索实验结果显示,OA组及K252a组大鼠跨越平台次数较正常对照组、假手术组、LY294002组及BDNF组明显减少(P＜0.01).Western blot结果表明,OA组、LY294002组、K252a组pThr231表达较正常对照组及BDNF组明显增多(P＜ 0.01),BDNF组与正常对照组比较无统计学差异(P＞ 0.05)；OA组和K252a组突触素表达较正常对照组、BDNF组及LY294002组明显减少(P＜0.01)结论 OA海马内注射可引起tau蛋白过磷酸化,从而导致突触结构功能障碍,引起大鼠空间认知障碍.外源性BDNF可通过激活TrkB受体补充缺乏的神经营养因子,减少tau过磷酸化,增加突触可塑性,促进突触形成,改善认知功能障碍.%Objective To observe the effects of exogenous brain-derived neurotrophic factor (BDNF) on the expression of synaptophysin in Alzheimer's disease (AD) rat's brain and the behavior of the rats,and explore the possible mechanisms. Methods A total of 60 healthy male Wistar rats,weighing 200 to 250 g,were randomly divided into the normal control group,false operation group,okadaie acid (OA) group,BDNF group,K252a group,and LY294002 group. With the localization the hippocampal CA3 region in stereotaxic atlas of the rat brain,each side of hippocampal was injected with 2 μL saline for false operation group rats,2 μL OA (0.2 μmol/L) for OA group;2 μL OA+2 μL BDNF (50 ng/mL) for BDNF group,2μL OA+2 μL BDNF+2 μL K252a (4 (μmol/L) for K252a group,and 2 μL OA+2 (μL BDNF+2 μL LY294002 (4 μmol/L) for LY294002 group. Behavior changes of rats were measured with the waler maze tesl. Western blot was applied to detect the expression of pThr231 and synaptophysin. Results Directional navigation experiment: the escaping latencies of OA and K252a group were significantly prolonged than the normal control group, sham operation group, LY294002 group and BDNF group (P < 0.01 );the escaping latencies of BDNF and LY294002 were also significantly prolonged than the normal group and sham operation group (P < 0.01); there was no significant difference between normal group and sham operation group (P > 0.05). Space exploration experiment: the acrossing platform frequency of OA and K252a group were significantly less than the normal group,sham operation group,LY294002 group and BDNF group (P < 0.01 ). The pThr231 expression in OA and l,Y294002/K252a group were significantly higher than in the normal con-trol group and RDNF group ( P < 0.01 ) ; belween BDNF group and normal control group, there was no significant difference ( P > 0.05 );rnSYN expression in K252a and OA group was significantly reduced compared with the normal control group,BDNF group and LY294002 group ( P < 0.01 ). Conclusion Injection of OA in hippocampal can cause tau protein phosphorylation, leading to synaptic dysfunction, and further cause disturbance of spatial cognition in rats. Exogenous BDNF can improve cognitive impairment through activating TrkB receptor to supplement the lack of neurotrophic factor, reduce tau phosphorylation, increase synaptic plasticity, and promote synapse formation.