异氟醚预处理通过上调海马 AMPA 受体GluR1亚基表达改善局灶性脑缺血再灌注损伤大鼠学习记忆功能

目的：探讨异氟醚预处理对脑缺血再灌注损伤大鼠学习记忆的影响及其可能机制。方法36只雄性成年Sprague-Daw ley大鼠，采用随机数字表法分为假手术组、缺血再灌注组和异氟醚预处理组，每组12只。采用改良线栓法制作大脑中动脉闭塞（ middle cerebral artery occlusion, MCAO）脑缺血再灌注模型。异氟醚预处理组每天吸入1.5％异氟醚1 h，连续5 d，末次预处理后24 h制作MCAO模型。 MCAO后24 h时采用2,3,5-氯化二苯四氮唑染色检测脑梗死体积；MCAO后1、3、7和14 d时进行改良神经功能缺损程度评分（modified Neurological Severity Score, mNSS ）；MCAO后9 d时采用水迷宫实验评价大鼠学习记忆；14 d时采用蛋白质印迹法检测缺血侧海马组织谷氨酸受体1（glutamate receptor 1, GluR1）蛋白表达水平。结果假手术组大鼠未见明显梗死灶，异氟醚预处理组大鼠梗死体积较脑缺血再灌注组显著缩小[（26.383±3.128）％对（19.107±1.661）％；P<0.05]。假手术组未见神经功能缺损（0分），异氟醚预处理组MCAO 后1、3、7和14 d时mNSS评分较缺血再灌注组均显著降低[1 d：（9.000±1.195）分对（11.500±1.414）分；3 d：（6.625±1.407）分对（6.625±1.407）分；7 d：（5.875±0.707）分对（7.375±1.407）分；14 d：（3.375±1.187）分对（5.125±1.246）分；P均＜0.05]。水迷宫实验显示，异氟醚预处理组MCAO 后1~5 d时逃避潜伏期分别为（95.992±15.734） s、（70.949±14.708） s、（39.660±7.413） s、（22.692±5.778） s和（14.906±4.336）s，显著短于缺血再灌注组的（103.008±11.654）s、（94.705±14.709）s、（65.716±10.155）s、（35.240±8.553）s和（22.890±10.381）s（P均<0.05）。异氟醚预处理组穿越平台次数和目标象限停留时间百分比为（4.556±1.333）次和（33.014±5.223）％，显著多于和高于脑缺血再灌注组的（2.889±1.536）次和（21.978±6.697）％（P均＜0.01）。假手术组、脑缺血再灌注组和异氟醚预处理组缺血侧海马GluR1蛋白水平分别为0.871±0.153、0.456±0.130和0.689±0.126，3组间存在显著性差异（ F=18.329，P<0.001），异氟醚预处理组显著高于缺血再灌注组（ P<0.05）。结论异氟醚预处理可改善脑缺血再灌注大鼠的学习记忆，其机制可能与上调海马组织G luR1表达有关。

Isoflurane preconditioning improves learning and memory functions in focal cerebral ischemia-reperfusion injury in rats by upregulating hippocampal AMPA receptor GluR1 subunit

Objective To investigate the effect of isoflurane preconditioning on rat learning and memory in cerebral ischemia-reperfusion injury and its possible mechanism.Methods Thirty-six adult male Sprague-Daw ley rats w ere randomly divided into a sham operation group, a cerebral ischemia-reperfusion group, and an isoflurane preconditioning group (n=12 in each group). A model of middle cerebral artery occlusion and ischemic-reperfusion w as induced by a modified intraluminal suture method. The rats of the isoflurane preconditioning group inhaled 1.5%isoflurane for 1 hour per day for 5 d. At 24 h after the last preconditioning, a model of MCAO w as made. At 24 h after MCAO, the infarct volume w as detected by using 2,3,5 chlorinated diphenyl tetrazolium staining. At day 1, 3, 7, and 14 after MCAO, the modified Neurological Severity Score (mNSS) were performed. At day 9 after MCAO, the Morris w ater maze test w as used to evaluate the learning and memory of rats. At day 14, Western blotting w as used to detect the protein expression level of hippocampal tissue glutamate receptor 1 (GluR1) on the side of ischemia. Results No obvious infarcts w ere observed in the rats of the sham operation group. The infarct volume in the isoflurane preconditioning group w as significantly smal er than that of the cerebral ischemia-reperfusion group (26.383%±3.128%vs.19.107%±1.661%;P<0.05). No neurological deficit w as observed in the sham operation group (score 0). The mNSS scores at day 1, 3, 7, and 14 after MCAO in the isoflurane preconditioning group w ere decreased significantly (day 1:9.000 ±1.195 vs.11.500 ±1.414;day 3:6.6250 ±1.407 vs.6.625 ±1.407vs.6.625 ±1.407; day 7: 5.875 ±0.707 vs.7.375 ±1.407; and day 14:3.375 ±1.187 vs.5.125 ±1.246;al P<0.05). The Morris w ater maze show ed that the escape latencies at day 1-5 after MCAO in the isoflurane preconditioning group w ere al significantly shorter than those in the cerebral ischemia-reperfusion group (day 1: 95.992 ±15.734 s vs.103.008 ±11.654 s; day 2: 70.949 ±14.708 s vs. 94.705 ±14.709 s;day 3:39.660 ±7.413 s vs.65.716 ±10.155 s;day 4:22.692 ±5.778 s vs.35.240 ±8.553 s;day 5: 14.906 ±4.336 s vs.22.890 ±10.381 s; al P<0.05). The numbers of crossing platform (4.556 ± 1.333 vs.2.889 ±1.536 ) and the percentages of time spent in the target quadrant ( 33.014%±5.223%vs. 21.978%±6.697%) in the isoflurane preconditioning group w ere significantly increased than in the cerebral ischemia-reperfusion group (al P<0.01). The levels of hippocampal GluR1 protein on the ischemic sides in the sham operation group, ischemia-reperfusion group, and isoflurane preconditioning group w ere 0.871 ±0.153, 0.456 ±0.130, and 0.689 ±0.126, respectively. There w ere significant differences among the 3 groups ( F=18.329, P<0.001) and the isoflurane preconditioning group w as significantly higher than the ischemia-reperfusion group (P<0.05). Conclusions Isoflurane preconditioning can improve the learning and memory in cerebral ischemia-reperfusion in rats, its mechanism may be associated w ith the uprelagating GluR1 expression in the hippocampus.