延迟亚低温对自发性高血压大鼠永久性大脑中动脉闭塞作用的研究

Effect of Mild Delayed Hypothermia on the Middle Cerebral Artery Occlusion in Spontaneously Hypertensive rats

目的建立自发性高血压大鼠(SHR)永久性大脑中动脉闭塞模型(pMCAO),观察亚低温对神经损伤的保护作用。方法将33只SHR随机分为①延迟2 h亚低温组[n=8,术后2 h给予(33±0.5)℃的全身亚低温];②延迟6 h亚低温组[n=9,术后6 h给予(33±0.5)℃的全身亚低温];③常温组(n=8,术后置于室温25℃);④假手术组(n=8,术中不插入线栓,术后置于室温25℃)。采用线栓法制作pMCAO模型。术后5 h,24 h,36 h对SHR进行神经行为学评分;并于术后36 h处死大鼠,制作脑冠状切片,尼氏染色后计算脑梗死体积、水肿程度;NeuN染色比较大鼠脑梗死周边和梗死核心区神经元的脱失。结果各组大鼠脑梗死后神经行为学评分差异无统计学意义。延迟2 h、6 h亚低温组的梗死体积分别较常温组减小23.75%(P<0.01)、18.72%(P<0.05);水肿程度减轻25.32%、21.52%(P<0.05)。神经元脱失情况:皮质梗死周边,延迟2 h、6 h亚低温组较常温组分别减少21.67%(P<0.01)、15.67%(P<0.05);而皮质梗死核心各手术组之间无明显差别。两亚低温组之间梗死体积、水肿程度及梗死周边神经元的脱失均无显著差异。结论亚低温治疗可以显著减小脑梗死体积和水肿程度。延迟6 h和延迟2 h亚低温治疗的效果无明显差异。

Aim To establish a permanent middle cerebral occlusion （pMCAO） model in spontaneously hypertensive rats （SHR） and investigate the neuroprotective effect of mild hypothermia therapy on neural lesion. Methods 33 SHR were randomly divided into four groups： 2 hours delayed mild hypothermia group; 6 hours delayed mild hypothermia group, normal temperature group and sham group. The pMCAO model was established by suture-occluded method. Systemic mild hypothermia （33 ± 0.5）℃ were induced on SHR 2 hours or 6 hours after pMCAO, and lasted for more than 30 hours. The objects were placed in room temperature（25 ℃ ）. The neurological behavior impairment was evaluated at 5 hours, 24 hours and 36 hours after the operation. Allsubjects were killed 36 hours after operation. Continuous coronal brain sections were stained by cresyl violet for the calculation of infarct volume and evaluation of brain edema. NeuN staining was used to detect the loss of neurons in the infarct and peri-infarct areas. Results There were no significant differences in neurological behavioral score among the ischemic groups. Compared with the control group, 2 hours delayed mild hypothermia and 6 hours delayed mild hypothermia decreased infarct volume by 23.75%（P〈0.01） and 18.72%（P〈0.05）, respectively. And the two mild hypothermic therapy alleviated brain edema by 25.32% （P〈0.05） and 21.52% （P 〈0.05）, respectively. In peri-infarct area, 2 hours delayed mild hypothermia group and 6 hours delayed mild hypothermia group had an increased count of NeuN positive cells compared with the normal temperature group. The two different hypothermia therapies decreased Neuron loss by 21.67%（P〈0.01） and 15.67%（P〈0.05）, respectively. In infarct core, no differences had been found in the number of NeuN positive cells among mild hypothermic groups and normal temperature group. There were no significant differences in infarct volume, brain edema and NeuN positive cells in peri-infarct area between the hypothermic groups. Conclusion Mild hypothermia could obviously decrease the infarct volume and brain edema after pMCAO. 6 hours delayed mild hypothermia therapy had the similar function with 2 hours delayed mild hypothermia.