Pinard E, Engrand N, Seylaz J
Department of Cerebrovascular Research, CNRS UPR 646, University of Paris 7, France.
J Cereb Blood Flow Metab. 2000 Dec;20(12):1648-58. doi: 10.1097/00004647-200012000-00004.
The diameter of surface microvessels and the erythrocyte velocity and flux through intraparenchymal capillaries in the parietal cortex were measured during transient global cerebral ischemia and reperfusion using laser-scanning confocal fluorescence microscopy in anesthetized rats. The role of nitric oxide (NO) from neurons in the microcirculatory changes was also investigated using 7-nitro-indazole (7-NI, 25 mg/kg, i.p.). Wistar rats (4 per group) equipped with a closed cranial window were given fluorescein isothiocyanate (FITC)-Dextran and FITC-labeled erythrocytes intravenously to respectively visualize the microvessels and the erythrocytes in the capillaries. Experiments were videorecorded on-line. Forebrains were made ischemic for 15 minutes and then reperfused for 120 minutes under the microscope. Ischemia was associated with a flattened EEG, a low persistent blood flow, and a transient leakage of fluorescein across the arteriole wall. Unclamping the carotid arteries led to immediate high blood flow in the arterioles, but it was not until 5 minutes later that the arterioles dilated significantly (181% +/- 27%) and erythrocyte velocity in the capillaries increased significantly (460% +/- 263%). Neither nonperfused capillaries nor erythrocyte capillary recruitment occurred. 7-Nitro-indazole significantly reduced the arteriole dilatation and prevented the increase in erythrocyte velocity and flux through capillaries in early reperfusion. 7-Nitroindazole had no influence on the fluorescein leakage. The current study suggests a partial role for NO released from neurons in the postischemic microcirculatory changes and provides new findings on the timing of arteriole dilatation and blood-brain barrier opening, and on erythrocyte capillary circulation in global ischemia.
在麻醉大鼠中，利用激光扫描共聚焦荧光显微镜，在短暂性全脑缺血和再灌注期间测量顶叶皮质表面微血管的直径、实质内毛细血管中红细胞的速度和通量。还使用7-硝基吲唑（7-NI，25mg/kg，腹腔注射）研究了神经元释放的一氧化氮（NO）在微循环变化中的作用。给装有闭合颅骨窗的Wistar大鼠（每组4只）静脉注射异硫氰酸荧光素（FITC）-葡聚糖和FITC标记的红细胞，以分别观察微血管和毛细血管中的红细胞。实验进行在线视频记录。在显微镜下，使前脑缺血15分钟，然后再灌注120分钟。缺血与脑电图平坦、持续性低血流以及荧光素跨动脉壁的短暂渗漏有关。松开颈动脉导致小动脉立即出现高血流，但直到5分钟后小动脉才显著扩张（181%±27%），毛细血管中的红细胞速度显著增加（460%±263%）。未出现无灌注毛细血管和红细胞募集至毛细血管的情况。7-硝基吲唑显著减少了小动脉扩张，并阻止了再灌注早期红细胞速度和通过毛细血管通量的增加。7-硝基吲唑对荧光素渗漏无影响。本研究表明神经元释放的NO在缺血后微循环变化中起部分作用，并提供了关于小动脉扩张和血脑屏障开放的时间以及全脑缺血时红细胞毛细血管循环的新发现。
