大鼠脑缺血后1H磁共振波谱分析的实验研究

目的:1H磁共振波谱(1HMRS)分析大鼠大脑中动脉梗塞后1周脑内代谢物的动态变化,并随访2个月.方法:18只Wistar大白鼠随机分为正常对照组,假手术组和永久性脑缺血组,每组各6只.脑缺血组右侧颈内动脉栓塞制作永久性脑缺血模型.采用1H磁共振波谱(1HMRS)于脑缺血后30min、1、3、6、12、24h、3、7、15d、1、2月对梗塞区域和对侧半球相应区域进行代谢物的波谱分析.结果:正常对照组和假手术组双侧代谢物无异常改变,分布对称(P＞0.05);脑缺血组梗塞区与对照区N-乙酰基天门冬氨酸(N-acetyl-aspartate,NAA),胆硷(choline,Ch)和肌酸(creatine,Cr)均于脑缺血后30min开始升高,3～6h后逐渐降低,但梗塞区与对照区NAA,Ch和Cr没有显著性差别(P＞0.05),24h双侧NAA达最低水平,Ch和Cr于3天后降到最低,随缺血时间的延长,NAA,Ch和Cr逐渐增加,尤其是NAA增加最明显,2个月时NAA较24h增加2.5倍(P＜0.01).患侧最早于脑缺血后10min检测到乳酸(lactate,Lac),随后Lac持续增加3天后开始降低.随访中未发现Lac再次升高.结论:(1)1H MRS能及早反映动物脑缺血后脑内代谢物的改变.(2)1HMRS能客观反映脑缺血慢性期脑内代谢物的异常,为临床评价脑保护药物疗效提供重要信息.

An experimental research in rat model of middle cerebral artery occlusion using 1 H MRS

Objective:To study the metabolic dynamic changes in rat model of permanent middle cerebral artery occlusion(MCAO) within one week,followed up for two months with 1H MRS.Methods:A total of 18 rats were randomized into three different groups,the normal( n =6),the sham-operated( n =6) and cerebral ischemic group ( n =6).A rat model of permanent MCAO was induced by occluding the right middle cerebral artery. 1H MRS was performed within the area of cerebral infarction and the homologous area of the contralateral hemisphere at the following time points:30min,1,3,6,12,24h,3,7,15d,1 and 2months after cerebral ischemia.Results:In the normal and the sham-operated group,bilateral metabolites were symmetrically distributed,no significant differences in NAA,Ch and Cr concentration were found between two hemispheres( P >0.05).The marked increase in NAA,Ch and Cr was recognizable in bilateral spectra 30min after cerebral ischemia and sustained up to the period of 3-6hours,there was no significant difference in NAA,Ch and Cr concentration between two hemispheres( P >0.05).NAA reached the lowest level at 24hours and Ch and Cr at 3days,and then NAA,Ch and Cr gradually increased with time.The increase in NAA was especially obvious which increased by 1.5 times at 2 months than that at 24hours after cerebral ischemia.The earliest detection of lactate was at 10 minutes within the infarct.The lactate concentration elevated and peaked at 12 hours,and a partial recovery of the reduction of lactate was seen at 3 days.However,the elevation in lactate was no longer observed during the period of up to 2 month follow-up.Conclusion:(1) 1HMRS can early detect the metabolite changes induced by middle cerebral artery occlusion in rats.(2).Abnormalities in chronic stage of cerebral ischemia in rats could also be found and gave important information for evaluating neuroprotective strategies.