乳化异氟醚预处理对大鼠局灶性脑缺血再灌注时海马腺苷A1受体表达的影响

Effect of emulsified isoflurane preconditioning on adenosine Al receptor expression in hippocampus during focal cerebral ischemia-reperfusion in rats

目的探讨乳化异氟醚预处理对大鼠局灶性脑缺血再灌注时海马腺苷A1（AA1）受体表达的影响。方法健康雄性sD大鼠88只，体重280～320g，采用随机数字表法，将其随机分为7组：假手术组（s组，n=16）、缺血再灌注组（I／R组，n：16）、乳化异氟醚预处理组（EI组，n=16）、乳化异氟醚溶剂组（LE组，n=16）、乳化异氟醚＋AAl受体拮抗剂8-环戊基-1，3-二丙基黄嘌呤（DPCPX）组（ED组，n=8）、DPCPX组（DP组，n=8）和DPCPX溶剂二甲基亚砜组（DM组，n=8）。采用大脑中动脉阻塞法制备局灶性脑缺血再灌注损伤模型。于缺血前24h，I／R组、EI组和LE组分别腹腔注射生理盐水、8％乳化异氟醚和脂肪乳剂10．5ml／kg，DP组和DM组分别腹腔注射DPCPX1mg／kg和二甲基亚砜2．5mg／kg，S组于相应时点腹腔注射生理盐水10．5ml／kg；ED组于腹腔注射8％乳化异氟醚前30min腹腔注射DPCPX1mg／kg。各组于再灌注24h时取8只大鼠，进行神经功能缺陷评分，然后处死，取脑组织，测定脑梗死体积；S组、I／R组、EI组和LF组于再灌注24h时处死8只大鼠，取脑组织，采用Western blot法检测海马AA1受体的表达水平。结果与s组比较，其余各组神经功能缺陷评分和脑梗死体积百分比升高，I／R组和LE组海马AAl受体表达下调，EI组海马AA1受体表达上调（P〈0．01）；与I／R组比较，EI组神经功能缺陷评分和脑梗死体积百分比降低，海马AAl受体表达上调（P〈0．05或0．01）；与EI组比较，LE组、ED组、DP组和DM组神经功能缺陷评分和脑梗死体积百分比升高（P〈0．05或0．01）。结论乳化异氟醚预处理减轻大鼠局灶性脑缺血再灌注损伤的机制可能与上调海马AA1受体表达有关。

Objective To investigate the effect of emulisified isoflurane preconditioning on adenosine A1 （AA1） receptor expression in hippocampus during focal cerebral ischemia-reperfusion （I/R） in rats. Methods Eighty-eight male adult SD rats weighing 280-320 g were randomly divided into 7 groups： sham operation group （group S, n = 16）, focal cerebral I/R group（group I/R, n = 16）, emulsified isoflurane preconditioning group （group EI, n = 16）, fat emulsion group （group LE, a = 16）, EI ＋ AA1 receptor antagonist DPCPX group （group ED, n = 8）, DPCPX group （group DP, n = 8） and DPCPX sovlent DMSO group （group DM, n = 8）. Focal ce- rebral I/R was induced by middle cerebral artery occlusin （MCAO） using a nylon thread with rounded tip inserted into internal carotid artery and advanced cranially until resistance was met. MCAO was maintained for 2 h followed by 24 h reperfusion. Normal saline, 8% emulsified isoflurane or fat emulsion 10.5 ml/kg was injected intraperito- neally in groups I/R,EI and LE respectively, and DPCPX 1 mg/kg or DMSO 2.5 mg/kg was injected intraperitone-ally in groups DP or DM at 24 h before MACO. In group DP DPCPX 1 mg/kg was injected intraperitoneally at 30 min before emulsified isoflurane injection. Neurologic function was evaluated and scored at 24 h of repcrfusion （0 = no deficit,4 = unable to crawl, loss of consciousness） and then the rats were sacrificed, their brains were re- moved for determination of infarct volume percentage. The hippocampal AA1 receptor expression was detected by Western blot at 24 h of reperfusion in groups S, I/R, El and LE. Results Focal cerebral I/R significantly increased the neurologic dysfunction score and infarct volume percentage, and decreased AA1 receptor expression in group I/ R as compared with group S. Emulsified isoflurane preconditioning could reduce I/R-induced increase in neurologic dysfunction score and infarct volume percentage and decrease in AA1 receptor expression in group EI as compared with group I/R. Emulsified isoflurane preconditioning-induced cerebral protection against I/R was significantly suppressed by AA1 receptor antagonist DPCPX in group DP. Conclusion Emulsified isoflurane preconditioning can attenuate cerebral I/R injury by up-regulating AA1 receptor expression in hippocampus.