Study On Early Cerebral Blood Flow Changes In Rat Middle Cerebral Artery Occlusion Model

Stroke is a worldwide medical emergency which is seriously threateninghuman health due to its high rate of morbidity, mortality and disability, andgains a lot of attention in the medical profession. Intraluminal filamentmiddle cerebral artery occlusion (MCAO) model in rats has been widely usedto mimic human ischemic stroke and serves as an indispensable tool in thestroke research field due to its noninvasive and reversible features. Thecerebral blood flow (CBF) information after cerebrovascular occlusion mayreflect the availability of collateral circulation, and physiology and pathologyof brain tissues, which serves as a key indicator in stroke models. By utilizinglaser speckle contrast imaging (LSCI), we can obtain high spatio-temporalfull-field imaging of CBF without scanning.In this paper, we investigated the spatio-temporal changes of CBF in rat MCAO stroke model using our self-developed real-time LSCI system. CBFimages of adult male Sprague Dawley rats (N=12) were recorded beforesurgery as baseline, during first1.5hours after surgery, and at24hours afterstroke. We compared the CBF changes after stroke surgery and got the resultsas below:(1) In the ipsilateral hemisphere, CBF of the vein and the arterydecreased to45%and30%of baseline, then recovered15%and5%respectively, and was42%and32%at24hours after the surgery, while CBFof the vein kept above baseline after occlusion in the contralateralhemisphere.(2) Diameters of the veins in ipsilateral and contralateral hemispheresvaried after the stroke surgery. The diameter of ipsilateral vein reduced atfirst and then increased gradually, and remained below baseline at the24hours after surgery, while the diameter of contralateral vein remained abovebaseline post ischemia.(3) There was a high correlation between the brain infarct volume24hours after ischemia and the CBF reduction during the first30minutes afterMCA occlusion. When50%of CBF reduction was set as threshold, thecorrelation coefficient between its corresponding cortex area and the infarctvolume reached the maximum at the first minute after occlusion （R~2=0.540, p <0.05）. When25%was set as threshold, the correlation coefficientachieved the maximum value at the30th minute after occlusion （R2=0.571，p <0.05）.Our observations provide valuable information in understanding theCBF spatio-temporal changes during early stage of rat MCAO model. Thecorrelation between CBF variation and brain infarct volume shows that CBFreduction immediately after the filament occlusion can be used as a predictorof brain injury size. Moreover, LSCI may help with the guidance of surgeryprocedure so as to improve the consistency of rat MCAO stroke models.