APP/PS1双转基因小鼠早期记忆功能障碍与胆碱能系统的关系研究

目的观察转APP/PS1基因阿尔茨海默病小鼠(APP/PS1小鼠)早期空间学习记忆功能及乙酰胆碱能系统的变化以及两者之间的相关性,探讨阿尔茨海默病早期学习记忆障碍的发病机制。方法应用Morris水迷宫法评定3月龄APP/PS1小鼠及相应野生型(WT)小鼠的空间学习记忆功能;采用免疫组织化学及组织化学染色方法检测脑组织中β-淀粉样蛋白(Aβ)斑块沉积情况;采用ELISA法检测脑组织中乙酰胆碱(ACh)含量以及胆碱乙酰转移酶(ChAT)和乙酰胆碱酯酶(AChE)活性,并探讨小鼠脑组织中ACh含量与其空间记忆能力、ChAT活性的相关性。结果水迷宫评定结果显示两组小鼠到达平台的潜伏期无统计学差异(P>0.05);APP/PS1小鼠在目标象限的游泳时间百分比〔(29.02±4.27)%〕和距离百分比〔(28.85±3.77)%〕较WT小鼠均下降(P<0.05)。APP/PS1小鼠脑组织中尚无Aβ斑块的沉积。APP/PS1小鼠脑组织中ACh含量〔(45.23±1.40)ng/g prot〕和ChAT活性〔(279.53±12.13)U/g组织湿重〕均较WT小鼠〔分别为(54.08±4.84)ng/gprot、(315.84±11.32)U/g组织湿重〕显著降低(P<0.05),两组小鼠脑组织中AChE活性无统计学差异(P>0.05)。小鼠脑组织中ACh含量与其空间记忆功能(目标象限航行时间百分比、目标象限航行路程百分比)呈正相关(r=0.861、r=0.874,P<0.05),ACh含量与ChAT活性呈正相关(r=0.926,P<0.05)。结论 APP/PS1小鼠空间记忆功能障碍、ACh含量减少和ChAT活性降低可发生于Aβ斑块沉积之前。脑组织中ACh含量减少和ChAT活性降低可能与APP/PS1小鼠记忆功能损害密切相关。

Relationship between early memory impairment and acetylcholine in a transgenic mouse model of Alzheimer disease

Objective To investigate the relationship between the spatial cognitive ability and the changes of cholinergic system,and elucidate the mechanism of cognitive deficits in the early stage of a transgenic APP/PS1 mouse model of Alzheimer’s disease(APP/PS1 mice). Methods The spatial learning and memory ability were assessed by Morris water maze test.In the APP/PS1 and wild type(WT) mice,the beta-amyloid(Aβ) plaques were detected by immunohistochemistry and histochemistry,and the content of ACh and the activity of ChAT and AChE in brain tissues were measured by ELISA.The relationship between ACh content in mice brain tissue and the spatial memory ability,and the relationship between ACh content and ChAT activity were analyzed by linear regression and correlation analysis method. Results No significant difference in the escape latency was observed between two groups(P>0.05),but the time (29.02±4.27)%] and distance (28.85±3.77)%] spent in the target quadrant significantly declined in the APP/PS1 mice comparing with the WT mice(P<0.05),indicating the normal spatial learning ability and impaired spatial memory ability in the 3 month APP/PS1 mice.No Aβ plaque was detected in the brain tissue in 3 month APP/PS1 mice by histopathology.ACh content (45.23±1.40) ng/g prot] and ChAT activity (279.53±12.13) U/g wet] significantly declined(54.08±4.84) ng/g prot,(315.84±11.32) U/g wet] in the APP/PS1 mice than in the WT mice(P<0.05),while the activity of AChE in the APP/PS1 mice was not significantly different than in the WT mice(P>0.05).Further analysis revealed that the spatial memory ability of the mice was positively correlated with the ACh content(r=0.861,r=0.874,P<0.05).The content of ACh was positively correlated with activity of ChAT(r=0.926,P<0.05). Conclusions The spatial memory impairment,declined ACh content and ChAT activity appeared before Aβ plaque deposition in 3-month APP/PS1 mice,and the declined ACh content and ChAT activity in brain tissue were greatly correlated with memory impairment,suggesting that impaired cholinergic system in brain tissue caused by soluble Aβ might play an important role in the development of memory deficits in the early stage of Alzheimer’s disease(AD),and reducing content of soluble Aβ and improving the damage of cholinergic system might be potential strategies for prevention and treatment of AD.