鼻咽腔降温对大鼠全脑缺血-再灌注损伤的保护作用

Effect of nasopharyngeal hypothermia on global cerebral ischemia-reperfusion injury in rats

目的探讨鼻咽腔降温对大鼠全脑缺血-再灌注损伤的保护作用。方法健康雄性Wistar大鼠18只,随机均分为三组:全身降温组(A组)、鼻咽腔降温组(B组)、常温组(C组)。采用Pulsinelli四血管阻断法建立大鼠全脑缺血-再灌注损伤模型。A、B组海马温度降至靶温度33℃,阻断双侧颈总动脉20min再灌注,低温维持1h后复温。C组保持大鼠直肠和海马温度均为(37±0.5)℃,阻断双侧颈总动脉20min再灌注。利用微透析技术收集大鼠海马CA1区微透析液并测其谷氨酸(Glu)含量。再灌注8h后断头取脑,用免疫组化法观察海马CA1区Bcl-2和Bax的表达。结果 A组海马温度从37℃降到33℃所需时间为B组的4.8倍;缺血10、20min、再灌注后10、20、30min时A、B组Glu含量明显低于C组(P<0.05);A、B、C组海马CA1区Glu含量恢复至缺血前水平所需时间分别为(19.92±1.30)、(20.17±1.34)、(39.67±1.49)min。与C组比较,A、B组的Bax免疫阳性细胞数显著减少(P<0.05);A、B组的Bcl-2免疫阳性细胞数显著增多(P<0.05)。结论鼻咽腔降温对大鼠全脑缺血-再灌注损伤具有保护作用,且鼻咽腔降温法降低海马温度的速度明显快于全身降温法。

Objective To investigate the effect of nasopharyngeal cooling on global cerebral ischemia-reperfusion injury in rats. Method Eighteen male Wistar rats weighing 200±50g were randomly divided into 3 groups（n=6）： Normal temperature group/group A; Whole body cooling group/group B; Nasopharyngeal cooling group/group C. By using the method of modified Pulsinelli’s four-vessel occlusion, the model of global cerebral ischemia-reperfusion injury was established in rats. Group A： both the rectal temperature and the hippocampal temperature were maintained at 37±0.5℃ by using a heated water blanket and an infrared lamp during the experiment. Group B： the hippocampal and the rectal temperature was reduced to 33℃ by using a fan and a ice bag. Group C： gel silica pipes were inserted into both nasal cavities to a depth of 5 mm, and cold physiologic saline （5℃） was infused at a rate of 100 mL？min-1？kg-1 until the hippocampal temperature decreased to 33℃. A cotton ball was placed in the lower pharynx and a suction device was placed for drainage, so as not to cause aspiration of saline. The rectal temperature was maintained at 37.0±0.5℃ using a heated water blanket and an infrared lamp. Arteria carotis communis were clamped for 20min when the hippocampal temperature was 33℃ in group B and group C, and the objective temperature was maintained for 60 mins, and then rewarming was initiated with the use of heated water blanket and an infrared lamp. Dialysates in left hippocampal CA1 region were collected every 10 mins for 2h after onset of reperfusion. Rats were anesthetized again, and fixed with 4% PFA perfused via ascending aorta after reperfusion for 8h. The rats’ brain were carefully sampled and stored in 4℃ and used for immunohistochemical staining to observe the expression of Bcl-2 and Bax. Dialysates were stored under -70℃ and used to determine the concentration of glutamate by high performance capillary electrophoresis（HPCE）. Result It took 31±2.7min in group B and 6.5±0.7min in group C for reducing to 33℃ from 37℃ of hippocampus,. The onset latency in hippocampal temperature reducing 33℃ was 4.8 times longer than that in the nasopharyngeal cooling group; At 10min 、 20min of ischemia and 10min、20min、30min after ischemia the [Glu]e was significantly lower in both group B and group C compared with group A （P〈0.05）;The time of [Glu]e in hippocampal CA1 field returning to the level of control was 39.67±1.49min、19.92±1.30min、20.17±1.34min in group A、B and C respectively;The expression of Bax level in hippocampal CA1 field was significantly lower in both group B and group C compared with group A （P〈0.05）;The expression of Bcl-2 level in hippocampal CA1 field was significantly higher in both group B and group C compared with group A （P〈0.05）. Conclusion：Nasopharyngeal cooling protects brain from global cerebral ischemia-reperfusion same as whole body cooling does. The cooling speed of nasopharyngeal cooling method is more quicker than that of the whole body cooling method.