新生大鼠缺氧缺血性脑损伤程度与后期神经行为异常的关联

The correlation between the severity of hypoxic-ischemic brain damage in neonatal rats and subsequent abnormal neurobehavior

目的探讨评分法及磁共振成像(magnetic resonance imaging,MRI)判断大鼠缺氧缺血性脑损伤(hypoxic-ischemic brain damage,HIBD)程度并预测脑损伤后神经行为异常的意义。方法60只7日龄Sprague-Dawley(SD)大鼠采用随机数字表法分为对照组14只、假手术组14只、模型组32只。采用Rice-Vannucci法离断右侧颈总动脉+缺氧制作HIBD模型。模型组大鼠建模24 h内经一般情况评分及Longa评分联合评估,筛选出中、重度HIBD存活鼠进行实验。建模24 h随机选取5只模型组大鼠采用2,3,5-氯化三苯基四氮唑染色验证脑梗死;建模1周各组均随机选取6只大鼠采用苏木精-伊红染色镜下观察HIBD脑损伤情况;建模4周对照组和假手术组各随机选择4只、模型组取剩余的8只大鼠采用MRI进行脑损伤体积评估;建模5~6周对各组剩余8只大鼠采用圆筒实验、13周采用水迷宫实验检测大鼠神经行为。结果模型组32只大鼠经评估,共筛选出19只中、重度HIBD大鼠。模型组大鼠建模24 h经脑梗死验证均为中、重度HIBD,建模1周脑组织病理可见以灰质为主的脑损伤,4周时MRI显示中、重度HIBD比例为7/8。与对照组及假手术组相比,模型组建模5~6周圆筒实验左前肢使用率明显减少(P<0.05),建模13周水迷宫实验潜伏期明显延长(P<0.05),穿越平台象限次数明显减少(P<0.05)。建模24 h与4周模型组大鼠右脑损伤体积差异无统计学意义(P>0.05),建模4周MRI脑损伤体积与5~6周圆筒实验左前肢使用率、13周水迷宫实验穿越平台象限次数呈负相关(P<0.05),与13周水迷宫实验潜伏期呈正相关(P<0.05)。结论HIBD大鼠建模24 h内经一般情况评分及Longa评分可初步预测HIBD模型脑损伤程度,建模4周时在脑损伤慢性期通过MRI再次评估,对观测HIBD大鼠中、远期神经行为异常具有很好的预判作用。

Objective To assess the severity of hypoxic-ischemic brain damage(HIBD)in neonatal rats and predict the occurrence of subsequent neurobehavioral abnormalities after brain injury by scoring and magnetic resonance imaging(MRI).Methods 7-day-old of 60 Sprague-Dawley(SD)rats were randomly divided into control group(14 rats),sham operation group(14 rats)and HIBD model group(32 rats).HIBD model was established by right common carotid artery dissection with Rice-Vannucci method and hypoxia.Within 24 h after modeling,the rats in the model group were evaluated by general condition score and Longa score,and the surviving rats with moderate and severe HIBD were selected for the experiment.24 h after modeling,5 rats of the model group were randomly selected for 2,3,5-triphenyltetrazole chloride staining to verify cerebral infarction.1 week after modeling,6 rats from each group were randomly selected for hematoxylin-eosin staining to observe HIBD brain injury.4 weeks after modeling,4 rats were randomly selected from the control group and the sham operation group,and 8 rats from the remaining model group were used to evaluate the volume of brain damage by MRI.5-6 weeks after modeling,the remaining 8 rats from each group were subjected to the Cylinder test,and at 13 weeks,they underwent the Morris water maze test to evaluate their neurobehavior.ResultsIn HIBD model group,19 rats with moderate to severe HIBD were selected from 32 rats.24 h after modeling,cerebral infarction was verified in all rats,indicating moderate to severe HIBD.Brain tissue pathology observed 1 week after modeling revealed predominantly gray matter brain damage.MRI showed that 7 out of 8 rats had moderate to severe HIBD.Compared to the control and sham operation groups,the model group exhibited a significant decrease in the usage rate of the left forelimb in the Cylinder test at 5-6 weeks after modeling(P<0.05),and the latency period in Morris water maze test was significantly prolonged at 13 weeks after modeling(P<0.05),and the times of crossing platform quadrant were significantly reduced(P<0.05).There was no significant difference in the right brain injury volume between 24 h and 4 weeks model group(P>0.05).The brain injury volume in model group was negatively correlated with the usage rate of left forelimb in cylinder test at 5-6 weeks and the times of crossing platform quadrant in Morris water maze test at 13 weeks(P<0.05),and positively correlated with latency period in Morris water maze test at 13 weeks(P<0.05).Conclusions Within 24 h of HIBD modeling,the severity of brain injury can be preliminarily predicted by general condition score and Longa score.4 weeks after modeling,in the chronic phase of brain injury,MRI was proved to be an excellent predictor for mid-term and long-term neurobehavioral abnormalities in HIBD rats.