摘要目的:评价预先注射青年大鼠血浆对老龄大鼠脑缺血再灌注后认知功能障碍的影响及磷脂酰肌醇3-激酶/丝氨酸苏氨酸蛋白激酶(PI3K/Akt)信号通路在其中的作用。方法:SPF级健康雄性老龄SD大鼠72只，18月龄，体质量600~650 g，采用随机数字表法分为4组( n＝18)：对照组(C组)、脑缺血再灌注组(IR组)、预先注射青年大鼠血浆组(P组)和PI3K抑制剂LY294002组(LY组)。P组和LY组尾静脉注射青年大鼠血浆100 μl/次，C组和IR组尾静脉注射等容量生理盐水，2次/周，持续4周。然后IR组、P组和LY组在七氟烷麻醉下建立大鼠脑缺血再灌注损伤模型。麻醉前1 h时LY组尾静脉注射LY294002 0.3 mg/kg。再灌注后24 h时行神经功能缺损评分(Longa评分)，然后随机处死6只大鼠取脑组织，测定脑梗死体积。再灌注29 d时行旷场试验评估大鼠自发活动能力和焦虑样行为，再灌注30 d时行新物体识别实验评估大鼠认知功能。行为学测试结束后处死大鼠，分离海马组织，采用Western blot法测定磷酸化PI3K(p-PI3K)、磷酸化Akt(p-Akt)、突触后致密蛋白-95(PSD-95)和突触囊泡蛋白(SYN)的表达，测量海马CA1区神经元树突长度和树突棘密度。 结果:4组大鼠运动速度、路程以及旷场中心停留时间比较差异无统计学意义( P>0.05)。与C组比较，IR组、P组和LY组Longa评分和脑梗死体积升高，新物体探索百分比和辨别指数降低，海马组织p-PI3K、p-Akt、PSD-95和SYN表达下调，海马神经元树突长度和树突棘密度降低( P<0.05)；与IR组比较，P组Longa评分和脑梗死体积降低，新物体探索百分比和辨别指数升高，海马组织p-PI3K、p-Akt、PSD-95和SYN表达上调，海马神经元树突长度和树突棘密度增加( P<0.05)，LY组上述指标差异无统计学意义( P>0.05)；与P组比较，LY组Longa评分和脑梗死体积升高，新物体探索百分比和辨别指数降低，海马组织p-PI3K、p-Akt、PSD-95和SYN表达下调，海马神经元树突长度和树突棘密度降低( P<0.05)。 结论:预先注射青年大鼠血浆可减轻老龄大鼠脑缺血再灌注后认知功能障碍，其机制与激活海马PI3K/Akt信号通路，改善突触可塑性有关。

abstractsObjective:To evaluate the effect of pre-injection of young rat plasma on cognitive dysfunction after cerebral ischemia-reperfusion (I/R) in aged rats and the role of phosphatidylinositol 3-kinase/serine threonine protein kinase (PI3K/Akt) signaling pathway.Methods:Seventy-two SPF-grade healthy male Sprague-Dawley rats, aged 18 months, weighing 600-650 g, were divided into 4 groups ( n=18 each) by the random number table method: control group (group C), cerebral I/R group (group IR), pre-injection of young rat plasma group (group P) and PI3K inhibitor LY294002 group (group LY). In group P and group LY, young rat plasma 100 μl/time was injected via the tail vein. In group C and group IR, the equal volume of normal saline was injected via the the tail vein, 2 times a week for 4 weeks. Then the model of cerebral I/R injury was developed under sevoflurane anesthesia in IR, P and LY groups. LY294002 0.3 mg/kg was injected through the tail vein at 1 h before anesthesia in LY group. The neurological deficit score (Longa score) was performed at 24 h after reperfusion, and then 6 rats were randomly sacrificed, and brain tissues were obtained to determine the cerebral infarct volume. Spontaneous mobility and anxiety-like behavior were assessed by the open field test at day 29 of reperfusion, and cognitive function was assessed by the novel object recognition test at day 30 of reperfusion. At the end of the behavioral test, rats were sacrificed, hippocampal tissues were isolated for determination of the expression of phosphorylated PI3K (p-PI3K), phosphorylated Akt (p-Akt), postsynaptic dense protein-95 (PSD-95) and synaptic vesicle protein (SYN) (by Western blot), and the dendritic length and dendritic spine density of neurons in the hippocampal CA1 region. Results:There was no significant difference in motor speed, distance traveled, and time of staying at the center of the open field among the four groups ( P>0.05). Compared with group C, the Longa score and cerebral infarct volume were significantly increased, the percentage of novel object exploration and discrimination index were decreased, the expression of p-PI3K, p-Akt, PSD-95 and SYN in hippocampal tissues was down-regulated, and the dendritic length and dendritic spine density of hippocampal neurons were decreased in IR, P and LY groups ( P<0.05). Compared with group IR, Longa score and cerebral infarct volume were significantly decreased, the percentage of novel object exploration and discrimination index were increased, the expression of p-PI3K, p-Akt, PSD-95 and SYN in hippocampal tissues was up-regulated, and the dendritic length and dendritic spine density of hippocampal neurons were increased in group P ( P<0.05), and no significant change was found in the parameters mentioned above in group LY ( P>0.05). Compared with group P, Longa score and cerebral infarct volume were significantly increased, the percentage of novel object exploration and discrimination index were decreased, the expression of p-PI3K, p-Akt, PSD-95 and SYN in hippocampal tissues was down-regulated, and the dendritic length and dendritic spine density of hippocampal neurons were decreased in group LY ( P<0.05). Conclusions:Pre-injection of young rat plasma can attenuate cognitive dysfunction after cerebral I/R in aged rats, and the mechanism is related to activation of hippocampal PI3K/Akt signaling pathway and improvement in synaptic plasticity.