异丙酚对大鼠大脑功能和TPA、MMP9表达的影响

Effects of propofol on rat brain function and tPA/MMP9 expression

目的:探讨异丙酚对新生大鼠海马组织型纤溶酶原激活物(tissue-type plasminogen activator,tPA)和基质金属蛋白酶9(matrix metalloproteinase 9,MMP9)表达的影响及其与认知功能的关系。方法:新生7日龄大鼠随机分为3组:对照(CON)组为连续7 d腹腔注射生理盐水;异丙酚单次麻醉(SP)组为连续腹腔注射生理盐水6d,第7天注射异丙酚;异丙酚多次麻醉(RP)组为连续7 d腹腔注射异丙酚。各组随机取6只大鼠行血糖和血气监测。于建模后2 h、24 h、48 h、72 h和30 d各组随机取大鼠分离海马组织。其余大鼠喂养至出生后25 d行Morris水迷宫实验,测定其空间学习记忆能力。HE染色及尼氏染色观察海马形态学改变。采用Western blot法检测tPA和MMP9蛋白表达的动态变化,RT-PCR法测定tPA和MMP9的mRNA表达改变。结果:与CON组相比,RP组各时点大鼠海马tPA和MMP9蛋白表达均呈明显的下降趋势(P<0.05);而SP组仅24 h时tPA表达呈下降趋势,其它时点下降趋势不明显,MMP9表达均无明显下降。与CON组相比,24 h时RP组海马tPA及MMP9的mRNA表达明显下调(P<0.05),而SP组下调不明显。Morris水迷宫实验第3天开始RP组的逃逸潜伏期较CON组和SP组延长(P<0.05),且RP组在原平台象限的探索时间及穿越原平台所在位置的次数较CON组和SP组减少(P<0.05),而CON组和SP组之间的差异无统计学显著性。与CON组相比,RP组海马神经细胞数量减少且排列紊乱,神经元内尼氏体明显减少,部分神经元出现变性及坏死。而SP组与CON组相比差异无统计学显著性。结论:多次异丙酚麻醉可导致新生大鼠远期认知功能障碍,其机制可能与海马tPA及MMP9的表达下调、海马神经元正常形态及功能破坏有关;而单次异丙酚麻醉无此作用。

AIM： To investigate the effects of propofol on the expression of tissue-type plasminogen activator（ tPA） and matrix metalloproteinase 9（ MMP9） in the hippocampus and the cognitive function in neonatal rats. METHODS： The 7-day-old rats were randomly divided into 3 groups： the rats in control（ CON） group were intraperitoneally injected with normal saline for 7 d; the rats in single dose of propofol anesthesia（ SP） group were intraperitoneally injected with normal saline for 6 d and with propofol on the 7th day; the rats in repeated dose of propofol anesthesia（ RP） group were intraperitoneally injected with propofol for 7 d. Blood glucose and blood gas analysis were tested in 6 rats of each group. The rats were randomly selected from each group to isolate the hippocampal tissues at 2 h,24 h,48 h,72 h and 30 d after the last injection. The spatial learning and memory functions of the other rats aged 25 d were determined by Morris water maze. The morphological changes of the hippocampus were observed by HE staining and Nissl＇s staining. The expression of tPA and MMP9 at mRNA and protein levels was determined by RT-PCR and Western blot. RESULTS： Compared with group CON,the protein expression of tPA and MMP9 in RP group was significantly decreased at each time point,while no significant decrease was observed in SP group except at the time point of 24 h. Compared with CON group,the mRNA expression of tPA and MMP9 was down-regulated obviously in RP group,which was not significantly down-regulated in SP group. From the 3rd training day of Morris water maze beginning,the escape latency was prolonged,and the space exploration time and the number of crossing the original platform location were reduced in RP group compared with CON group and SP group,while no significant difference was observed between CON group and SP group. Compared with CON group,the number of nerve cells reduced and nerve cells arranged in disorder in the hippocampus in RP group. Moreover,the number of Nissl body decreased significantly and finally developed into neuronal degeneration and necrosis in RP group,and no significant difference between SP group and CON group was observed. CONCLUSION： Repeated dose of propofol anesthesia leads to long-term cognitive dysfunction in neonatal rats,which may be related to the down-regulation of tPA and MMP9 expression and destruction of normal morphology and function of neurons in hippocampus,whereas single dose of propofol anesthesia has no such effects.