MICROCIRCULATION OF THE AREA POSTREMA - PERMEABILITY AND VASCULAR-RESPONSES
MICROCIRCULATION OF THE AREA POSTREMA - PERMEABILITY AND VASCULAR-RESPONSES
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DOI：
10.1161/01.res.65.2.417
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发表时间：
1989-08-01
影响因子：
20.1
通讯作者：
HEISTAD, DD
中科院分区：
文献类型：
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作者：
FARACI, FM;CHOI, J;HEISTAD, DD
后区是室周器官，在循环的神经体液调节中发挥重要作用。我们开发了一种检查体内后区微循环的渗透性和血管反应的方法。对麻醉大鼠的背侧脑干进行开颅手术，并用荧光显微镜观察到后部区域的血管。在对照条件下，在后部区域发生荧光素钠（MW，386）的外渗，但没有150 kDa（MW）异硫氰酸荧光素-葡聚糖的外渗。在对照条件下，脑干中没有荧光素或葡聚糖外渗。急性高血压对后区 150 kDa 右旋糖酐的屏障造成显着破坏，而脑干的破坏则很小。我们测试了这样的假设：后部区域对小分子的渗透性比脑干更大，并且这种渗透性可能伴随着独特的血管反应。腺苷和 ADP 的局部灌注对后区和背侧脑干的小动脉产生类似的剂量相关扩张。局部和静脉加压素对后区和脑干产生类似的剂量相关的血管收缩。大鼠的电子显微镜显示，在供应后部区域的小动脉中存在对辣根过氧化物酶的屏障，而后部区域的毛细血管中不存在辣根过氧化物酶的屏障。因此，1）在正常情况下，后区的微循环对相对较小的分子是可渗透的，并且在急性高血压期间比脑干更容易受到大分子屏障的破坏；2）尽管毛细血管通透性存在显着差异，但后区和脑干中血管张力的调节响应于多种刺激。
The area postrema is a circumventricular organ that plays an important role in neurohumoral regulation of the circulation. We have developed a method to examine permeability and vascular responses of the microcirculation of the area postrema in vivo. A craniotomy was performed over the dorsal brain stem in anesthetized rats, and blood vessels to the area postrema were visualized with fluorescent microscopy. Extravasation of sodium fluorescein (MW, 386), but not 150 kDa (MW) fluorescein isothiocyanate-dextran, occurred in the area postrema under control conditions. There was no extravasation of fluorescein or dextran in the brain stem under control conditions. Acute hypertension produced marked disruption of the barrier to 150 kDa dextran in the area postrema, compared with minimal disruption in the brain stem. We tested the hypothesis that the area postrema has greater permeability to small molecules than the brain stem and that this permeability might be accompanied by distinctive vascular responses. Topical suffusion of adenosine and ADP produced similar dose-related dilation of arterioles to area postrema and dorsal brain stem. Topical and intravenous vasopressin produced similar dose-related constriction of vessels to area postrema and brain stem. Electron microscopy in rats demonstrated that a barrier to horseradish peroxidase, which is absent in capillaries in the area postrema, is present in arterioles that supply the area postrema. Thus, 1) the microcirculation of the area postrema is permeable to relatively small molecules under normal conditions and is more susceptible than the brain stem to disruption of the barrier by large molecules during acute hypertension and 2) regulation of vascular tone in response to several stimuli in area postrema and brain stem, despite marked differences in capillary permeability.