Effects of chronic multiple stress on learning and memory and the expression of Fyn, BDNF, TrkB in the hippocampus of rats

Background The effect of chronic stress on cognitive functions has been one of the hot topics in neuroscience. But there has been much controversy over its mechanism. The aim of this study was to investigate the effects of chronic multiple stress on spatial learning and memory as well as the expression of Fyn, BDNF and TrkB in the hippocampus of rats. Methods Adult rats were randomly divided into control and chronic multiple stressed groups. Rats in the multiple stressed group were irregularly and alternatively exposed to situations of vertical revolution, sleep expropriation and restraint lasting for 6 weeks, 6 hours per day with night illumination for 6 weeks. Before and after the period of chronic multiple stresses, the performance of spatial learning and memory of all rats was measured using the Morris Water Maze （MWM）. The expression of Fyn, BDNF and TrkB proteins in the hippocampus was assayed by Western blotting and immunohistochemical methods. The levels of Fyn and TrkB mRNAs in the hippocampus of rats were detected by RT-PCR technique. Results The escape latency in the control group and the stressed group were 15.63 and 8.27 seconds respectively. The performance of spatial learning and memory of rats was increased in chronic multiple stressed group （P〈0.05）. The levels of Fyn, BDNF and TrkB proteins in the stressed group were higher than those of the control group （P〈0.05）. The results of immunoreactivity showed that Fyn was present in the CA3 region of the hippocampus and BDNF positive particles were distributed in the nuclei of CA1 and CA3 pyramidal cells as well as DG granular cells. Quantitative analysis indicated that level of Fyn mRNA was also upregulated in the hippocampus of the stressed group （P〈0.05）. Conclusions Chronic multiple stress can enhance spatial learning and memory function of rats. The expression of Fyn, BDNF and TrkB proteins and the level of Fyn mRNA are increased in the stessed rat hippocampus. These suggest that Fyn and BDNF/TrkB signal transduction pathways may participate in the process of the enhanced learning and memory durina chronic multiple stress.     

去势后大鼠海马结构一氧化氮合酶阳性神经元的变化

目的：观察去势后大鼠海马结构一氧化氮合酶（NOS）阳性神经元的变化。方法：用黄递酶组织化学染色方法观察切除双侧卵巢后雌后SD大鼠海马结构NOS阳性神经元的形态，分布的变化，并进行计算机图像分析。结果：去势后海马结构NOS阳性神经元分布变化有区域差异性；NOS阳性神经元在下托、海马（CA）一区邻近下托的部分、CA三区、CA四区（CA4）和齿状回（DG）数目明显减少，而在CA二区数目明显明显增多，CA4和DG的NOS阳性神经元平均密度降低，胞体的平均周长和平均截面积都明显减少。结论：雌激素可能通过影响海马结构NOS的表达来影响学习和记忆。     

慢性综合应激对大鼠海马CA3区nNOS和BDNF表达及行为学表现的影响

目的：观察慢性综合应激引起的大鼠海马CA3区的病理变化及相应的行为学改变，探讨抑郁的发病机制。方法：观察在应激的不同时程内，Wistar大鼠海马CA3区神经元型一氧化氮合成酶(nNOS)和脑源性神经营养因子(BDNF)蛋白表达的动态变化，同时观察大鼠行为学改变。结果：经慢性应激11d，海马CA3区nNOS蛋白表达增加，BDNF蛋白表达减少，探究行为减少，修饰行为受到抑制，排便量增加；应激21d，nNOS蛋白表达有逐渐降低的趋势，BDNF蛋白表达几乎消失，大鼠表现为抑郁状态。结论：慢性综合应激可能通过损伤大鼠海马引起大鼠的抑郁状态，提示脑损伤可能在抑郁发病机制中起重要作用，保护脑组织应成为抑郁新的治疗靶。     

牛磺酸拮抗铅对大鼠海马NOS阳性神经元数目的影响

Objective: To study taurine resist lead impact ability of learning and memory. Methods: Using NADPH-d histochemistry method to study the quantity change of the rat's NOS positive neuron in hippocampus , the rat in experiment sections which are feeded with distinct dosage lead acetate in drinking (0.02, 0.2g/L) and feed contain distinct dosage taurine (5, 10g/kg). Results: Taurine could increase NOS positive neuron quantity obviously in hippocampus of rat induced lead lesion. Conclusion: Taurine could resist lead impact ability of learning and memory obviously.     

何首乌对Aβ1-40诱导的大鼠海马神经元内BDNF表达的影响

目的：探讨Aβ1-40对海马CA1区神经元脑源性神经营养因子（brain—derived neurotrophic factor，BONY）表达的影响，以及何首乌对其的干预作用。方法：右侧海马微量注射Aβ1-40，观察海马BDNF的表达变化；并使用何首乌浸膏对大鼠模型进行干预治疗。动物存活30d后，用“Y”迷宫检测各组动物学习和记忆能力；采用免疫组织化学方法和Westem-blot检测海马CA1区神经元BDNF的表达；应用尼氏染色法观察海马CA1区神经元数目和形态。结果：Aβ1—40能够导致大鼠学会躲避电刺激所需的“尝试次数”明显增加；BDNF蛋白的表达明显下降，并可以在海马观察到Aβ1-40的沉积；CA1区的神经元出现胞体肿胀、排列散乱等形态改变，且使用何首乌对动物模型干预治疗30d后。大鼠的躲避电刺激所需的“尝试次数”明显下降；海马CA1区神经元BDNF表达明显上调。结论：使用Aβ1—40在体内能够下调海马CA1区神经元BDNF表达。何首乌干预治疗30d，能够改善动物的学习和记忆能力，并能减少Aβ1-40对海马CA1区神经元BDNF表达的抑制作用。     

急性最大电休克和慢性经耳电点燃癫痫对大鼠学习和记忆的影响

目的:探讨急性最大电休克和慢性经耳电点燃癫痫对大鼠学习和记忆的影响。方法:通过双耳夹给予大鼠电刺激(150mA,0.2s)诱发急性最大电休克(MES),而慢性经耳电点燃癫痫,是经双耳夹每24h给予大鼠一次亚惊厥剂量电刺激(40mA,0.2s)直至完全点燃。采用八臂迷宫(四臂放饵)研究大鼠空间学习能力和记忆再现能力。高效液相色谱分析法(HPLC)检测脑中组胺、γ-氨基丁酸(GABA)、谷氨酸的含量变化。结果:在学习过程中,与对照组相比,急性最大电休克仅增加了学习过程中的参考记忆错误次数,同时使大鼠海马内GABA含量增加。而慢性经耳电点燃癫痫在空间记忆再现过程中,大鼠工作记忆和参考记忆错误次数增加并且在完全点燃后持续近3周。慢性经耳电点燃癫痫大鼠在完全点燃24h后海马CA1区神经元发生退行性变化,同时使大鼠海马组胺含量减少。结论:不同种癫痫对认知功能的影响不同:(1)急性最大电休克损伤了空间学习能力,可能与异常的突触可塑性及海马内的GABA含量上升有关;(2)慢性经耳电点燃癫痫诱发了空间记忆再现障碍,可能与海马CA1区神经元的病理改变及海马内组胺含量的下降有关。     

丰富环境对大鼠学习记忆及海马CA1区脑源性神经营养因子表达的影响

目的 探讨丰富环境对Wistar大鼠学习记忆的影响及其脑源性神经营养因子(BDNF)机制.方法 20只3周龄Wistar大鼠随机分为丰富环境组和正常对照组,分别在丰富环境和正常环境喂养30d.Morris水迷宫实验评定其学习记忆能力,免疫组化检测海马CA1区BDNF的蛋白表达.结果 丰富环境组大鼠逃避潜伏期[(24.37±5.45)s]显著短于对照组[(31.28±5.39)s],差异具有显著性(P<0.05);丰富环境组跨越平台次数[(3.38±0.79)次]、平台象限游泳距离[(915.52±125.12)cm]明显多于对照组[(2.21±0.49)次、(468.67±70.29)cm],差异具有显著性(P<0.01);丰富环境组海马CA.区BDNF灰度值(128.79±8.45)明显小于正常对照组(142.57±9.36),差异具有显著性(P<0.05).结论 丰富环境明显增强大鼠的学习记忆能力,其可能是通过BDNF机制实现的.     

慢性低水平铅暴露对发育期大鼠海马NMDAR-1 mRNA表达的影响

目的：探讨发育期低水平铅暴露对大鼠学习记忆影响的分子机制。方法：采用原位杂交技术，研究低水平铅后发育期海马NMDA受体亚单位1（NMDAR－1）mRNA表达的变化。结果：铅暴露组大鼠海马区锥体细胞层NMDAR－1 mRNA与对照组相比在16d时CA1区、CA3区分别增加18．75％和13．2％（P＜0．05），而在齿状回颗粒细胞层表达却降低14．29％（P＜0．01）；在32、64d除齿状回野粒细胞层表达降低9．67％、10．67％外（P＜0．01）外，其余各海马区未见有明显的光密度变化。结论：发育期铅暴露能导致NMDAR－1 mRNA表达的改变，进而影响NMDAR－1的表达，这可能是铅暴露影响学习记忆的分子机制之一。     

尼莫地平抗急性铅染毒大鼠海马神经元损伤的形态学研究

目的：了解尼莫地平对急性铅染毒大鼠海马神经元损伤的干预作用。方法：48只2月龄SD大鼠随机等分为4组，即染铅组（40mg／kg PbAc）、尼莫地平组（1mg／kg Nim）、铅-尼莫地平组（40mg／kg PbAc＋1mg／kg Nim）和对照组（等量生理盐水），每日腹注1次，连续3d。用TUNEL法原位检测海马神经元凋亡情况，并用电镜观察海马神经元超微结构变化。结果：各组海马神经元凋亡指数由高到低依次为染铅组、铅-尼莫地平组、对照组和尼莫地平组，染铅能显著增高海马神经元凋亡指数（P〈0．01），尼莫地平与铅存在交互作用（P〈0．01），在铅染毒的前提下，尼莫地平能明显降低神经元凋亡指数。电镜观察显示，染铅组海马神经元有核固缩现象，而铅-尼莫地平组神经元未见明显异常。结论：急性铅染毒能引起海马神经元损伤，促进细胞凋亡；尼莫地平可能具有抗急性铅染毒海马神经元损伤的作用。     

吡格列酮对创伤性脑损伤大鼠海马神经元的保护作用及机制探讨

目的    研究吡格列酮对创伤性脑损伤（TBI）大鼠海马神经元和认知行为障碍的影响及其作用机制。方法    将SD大鼠24只制成大鼠左侧脑皮层顶叶损伤模型,并分为假手术组（Sham组）、脑损伤溶剂注射组（Vehicle组）、吡格列酮治疗组（Pio组）、吡格列酮+过氧化物酶增殖因子活化受体γ（PPARγ）阻断剂（T0070907）组（Pio+Ant组）。采用Morris水迷宫实验观察大鼠记忆认知行为,对大鼠脑损伤第15天脑冠状切片进行小胶质细胞、星形胶质细胞和神经元的OX 42、GFAP、NeuN免疫组化染色,计数海马CA1、CA2及CA3区的细胞数量。结果    Vehicle组与Sham组比较,大鼠的潜伏期和游泳轨迹延长,海马神经元数量减少(P均<0.01),NeuN免疫染色变浅,小胶质和星形胶质细胞活化且数量增多（P均<0.01）;Pio组与Vehicle组比较,大鼠潜伏期及游泳轨迹明显缩短（P均<0.05）,神经元存活数量增多（P<0.05）,NeuN蛋白表达增强, 小胶质和星形胶质细胞反应减轻、数量减少（P均<0.05）。结论    吡格列酮可以通过PPARγ通路减轻大鼠脑损伤导致的海马区炎性反应,保护神经元,提高TBI大鼠记忆认知功能。