Regional variations in the apparent diffusion coefficient and the intracellular distribution of water in rat brain during acute focal ischemia
Regional variations in the apparent diffusion coefficient and the intracellular distribution of water in rat brain during acute focal ischemia
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DOI：
10.1161/01.str.32.8.1897
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发表时间：
2001-08-01
期刊：
影响因子：
8.3
通讯作者：
Fenstermacher, JD
中科院分区：
文献类型：
--
作者：
Liu, KF;Li, FH;Fenstermacher, JD
背景和目的：脑动脉闭塞后，缺血组织水的表观扩散系数(ADC)迅速下降。这种急剧下降被认为是由细胞外液体的损失和细胞内液体的增加引起的。为验证后一种可能性，在大鼠局灶性脑缺血90min结束时，观察3个脑区ADC值的变化和几个细胞室的大小。方法：8只SD大鼠永久性闭塞大脑中动脉，另2只大鼠进行假闭塞。90分钟后生成ADC图，并立即对大脑进行灌注固定。根据ADC范围定义了三个感兴趣区(ROI)。结果：缺血90min后，假手术组大鼠大脑皮质和对侧缺血区(ROI-a)平均ADC值正常，同侧额顶叶皮质(ROI-b)平均ADC值降低25%，缺血侧尾壳核外侧区(ROI-c)平均ADC值降低45%。此时，神经束内肿胀的星形细胞胞体和肿胀的树突和星形细胞突起的体积分别为ROI-a和lt；ROI-b和lt；ROI-c。ROI-b组和ROI-c组分别有40%和60%的神经元缩小，ROI-c组比ROI-b组缩小约25%。结论：局灶性脑缺血时ADC值的降低可能不仅是细胞外液的急性丢失和伴随的细胞间肿胀，还可能是神经元同时萎缩的结果。
Background and Purpose-The apparent diffusion coefficient of water (ADC) rapidly drops in ischemic tissue after cerebral artery occlusion. This acute drop is thought to be caused by the loss of extracellular fluid and the gain of intracellular fluid. To test the latter possibility, changes in ADC and the size of several cellular compartments were assessed in 3 regions of rat brain at the end of 90 minutes of focal cerebral ischemia.Methods-One middle cerebral artery was permanently occluded in 8 Sprague-Dawley rats; sham occlusions were performed in 2 other rats. ADC maps were generated 90 minutes later, and the brains were immediately perfusion fixed. Three regions of interest (ROIs) were defined on the basis of ADC range. Various neuronal, astrocytic, and capillary compartments in each ROI were quantified with light and electron microscopy.Results-At the end of 90 minutes of ischemia, mean ADC was normal in the cortex of sham-operated rats and the contralateral cortex of ischemic rats (ROI-a), 25% lower in the ipsilateral frontoparietal cortex (ROI-b), and 45% lower in the ischemic lateral caudoputamen (ROI-c). At this time, the frequency of swollen astrocytic cell bodies and volume of swollen dendrites and astrocytic processes in neuropil were ROI-a < ROI-b < ROI-c. In ROI-b and ROI-c, 40% and 60% of the neurons, respectively, were shrunken; the shrunken neurons were approximate to 25% smaller in ROI-c than in ROI-b. In these areas, many capillary endothelial cells, pericytes, and perivascular foot processes were swollen.Conclusions-The initial lowering of ADC during focal ischemia probably is the result of not only the acute loss of extracellular fluid and concomitant swelling of various cellular compartments but also concurrent neuronal shrinkage.