| BackgroundAs its high incidence,high fatality rate and high recurrence rate,stroke is the first cause of death among Chinese residents at present,and causes serious burden to the society and families.Acute ischemic stroke(cerebral infarction)is the most common type of stroke,accounts for about 60% ~ 80% of the total cases.The strengthening of the study of its etiology,pathogenesis,prevention and treatment,can provide more alternative approaches to reduce the incidence and the rate of poor prognosis of acute ischemic stroke.It is a crucial factor to establish an animal model with better repeatable and better simulation of the pathological process of ischemic stroke for the research of related ischemic brain injury.The rat acute focal cerebral ischemia model with middle cerebral artery occlusion(MCAO)prepared by line plug method is the most commonly used model.The modeling method,infarction volume and neurological dysfunction are relatively stable,but there is still certain failure rate due to the lack of objective and convenient judgment.Laser Doppler flowmetry(LDF)can accurately monitor the change scope and the duration of relative regional cerebral blood flow(rCBF)during the modeling process.ObjectiveTo investigate whether the monitoring of cerebral blood flow with laser doppler can be used to evaluate the successful preparation of rat focal cerebral ischemia model with middle cerebral artery occlusion(MCAO)prepared by line plug method,and provide a more objective standard for the evaluation of the model preparation.MethodsWith the line plug inserted into the left internal cerebral artery of 30 SPF Wistar Hanrats at(16.0±0.5)mm,(18.0±0.5)mm and(20.0±0.5)mm respectly,three kinds of focal cerebral ischemia models(10 each)were prepared.All the experimental rats were scored with Longa neurobehavioral scale 6 h after the ischemia and reperfusion.And then,all the animals were divided into incomplete occlusion group,complete occlusion group and deep occlusion group according to whether the blood clots were found in skull base and the infarction was appeared in the middle cerebral artery territory after the whole brain was stained with 2,3,5-triphenyl tetrazolium chloride.The cerebral blood flow in the middle cerebral artery territory of each animal was monitored by Laser Doppler at the time of before and after blocking with the line plug inserted and reperfusion with the line plug pulled out and recorded for statistical analysis.The cerebral blood flow was expressed as the relative flow unit(perfusion unit,PU);The changes of the cerebral blood flow after occlusion and reperfusion were expressed as a percentage of that blood flow and those before occlusion.ResultsDuring the process of modeling,1 rats died,and the other in the incomplete occlusion group(n=9),in the complete occlusion group(n=15),and in the deep occlusion group(n=5).The depths of inserting of 8 rats in the incomplete occlusion group were about(16±0.5)mm,and the blood flow from the anterior cerebral artery to middle cerebral artery could not be prevented completely,the Longa score was evaluated 6 h after ischemia and ranged from 0 to 1,there were no blood clots in skull base and no infarction after TTC staining.The depths of inserting of 9 rats in the complete occlusion group were about(18±0.5)mm,and the anterior cerebral artery blood flow was completely blocked,the neurological dysfunction was significant after 6 h ischemia and the Longa score was ranged from 2 to 3,the blood clots in skull base were absent and the infarctions in middle cerebral artery territory were obvious after TTC staining.The depth of inserting of 5 rats in the deep occlusion group were about(20±0.5)mm,and the anterior cerebral artery bloodflow was also completely blocked,the neurological dysfunction was serious after 6 h ischemia and the Longa score was ranged from 3 to 4,there existed blood clots in skull base and obvious infarctions in middle cerebral artery territory after TTC staining.The cerebral blood flows after the line plug inserted compared with those before occlusion in the incomplete occlusion group,complete occlusion group and deep occlusion group were all decreased(94±17 vs 256±36,43±9 vs 286±44,44±6 vs 294±46,respective,all P<0.05),and the difference between groups was statistically significant(F = 56.57,P<0.01),Those in complete occlusion group and deep occlusion group were lower than that in incomplete occlusion group(all P<0,05),but the difference between deep occlusion group with complete occlusion group was not statistically significant(P>0.05);The percentages of cerebral blood flow after occlusion and before were(36.93±0.06)%,(15.09±0.02)%,(15.52±0.04)% respective,and the difference between groups was statistically significant(F = 39.14,P<0.01).The cerebral blood flow after reperfusion were213 ± 31,147 ± 17,96 ± 1,respectively,and the difference was also statistically significant(F=50.05,P<0.01),and the cerebral blood flow in deep occlusion group was less than that in complete occlusion group(P<0.05);The percentages of cerebral blood flow after reperfusion and before occlusion were(83.10±0.02)%,(51.83±0.05)%,(33.49±0.09)% respective,and the difference was also statistically significant(F=93.23,P<0.01).The changes of cerebral blood flow monitored by Laser Doppler change can be used as the criterion to confirm the successfully preparation of MCAO ischemia models,and had higher sensitivity and specificity than the neurobehavioral scores(93.33 vs 80.00,92.86 vs 78.57).ConclusionThe cerebral blood flow monitored by laser Doppler can be used as a real-time,convenient,micro invasive,objective and reliable standard to evaluate the successful preparation of rat MCAO models with line plug method,and had higher sensitivity andspecificity than the neurobehavioral scores. |
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