局灶性脑缺血大鼠顶叶皮质一氧化氮合酶表达与CT灌注成像

Expression of nitrix oxide synthase and CT perfusion in the parietal cortex after severe focal cerebral ischemia in rats

目的:观察重度局灶性脑缺血状态下大鼠顶叶皮质一氧化氮合酶(NOS)表达过程,探讨NOS阳性神经元表达与脑血流量的关系。方法:SD大鼠随机分为5组即正常对照组,假手术组,脑缺血1、6、24h组。线栓法建立大鼠脑缺血模型,多排螺旋CT灌注成像测量脑血流量,采用还原型尼克酰胺腺嘌呤二核苷酸黄递酶(NADPH-d)法,观察脑血流量低于20%正常值时顶叶皮质NOS表达。结果:与对照组比较,缺血1h组顶叶皮质NOS阳性神经元数量明显增多;与对照组及缺血1h组比较,缺血6h组顶叶皮质NOS阳性神经元数量明显下降;与对照组及缺血1h组比较,缺血24h组顶叶皮质NOS阳性神经元数量进一步减少并几乎消失,与脑缺血6h组比较,无显著差异。当血流量仅轻度下降时,顶叶皮质NOS阳性神经元表达并无明显变化。结论:缺血侧脑血流量低于正常值20%时,顶叶皮质NOS阳性神经元在缺血1h时显著增加,缺血6、24h急剧减少;缺血后NOS阳性神经元表达,不仅与缺血持续时间有关,还与缺血程度有关。

Objective： To investigate the expression and changes of nitric oxide synthase （NOS） in the parietal cortex after severe focal cerebral ischemia, and relationship between cerebral blood flow （CBF） and the number of NOS positive neurons. Methods： SD rats were randomly divided into five groups： （1） control group, （2） the sham operation group, （3） the focal cerebral ischemic 1 h group, （4） the focal cerebral ischemic 6 h group, and （5） the focal cerebral ischemic 24 h group. Ische- mic model was reproduced by intraluminal occludation of rat cerebral arteries and confirmed by CT perfusion imaging （CT- PI）. By means of NADPH-d histochemistry technique, the expression of NOS was detected in the ischemic parietal neurons whose CBF was 20% below the normal level. Results： Compared to the control, 1 hour ischemia lead to an obvious increase in the mean number of NOS positive neurons in the ischemic parietal cortex. When 6- and 24 hour occludations were performed, the NOS positive neurons in the parietal cortex were decreased evidently and almost disappeared without statistical difference between them, which occupied the significant difference compared both to normal and those in 1 h ischemic group. No obvious change was found in NOS expression with the presence of slight decrease of CBF. Conclusion： NOS expressing neurons in the parietal cortex after severe focal cerebral ischemia depend on ischemic time, and correlate tightly with the extent and duration of the cerebral ischemia.