THE BLOOD-BRAIN-BARRIER
THE BLOOD-BRAIN-BARRIER
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DOI：
10.1038/scientificamerican0986-74
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发表时间：
1986-09-01
影响因子：
3
通讯作者：
BETZ, AL
中科院分区：
文献类型：
--
作者：
GOLDSTEIN, GW;BETZ, AL
在人类和其他复杂的生物体中，生命本身依赖于体内平衡，即维持恒定的内部环境。这种依赖性在大脑中最为明显。在身体的其他部位，激素、氨基酸和钾等离子的细胞外浓度会频繁地发生小幅波动，尤其是在进餐或运动后。如果大脑受到这种波动的影响，结果可能是神经活动不受控制，因为一些激素和氨基酸充当神经递质，而钾离子会影响神经细胞放电的阈值。因此，大脑必须与血液成分的短暂变化严格隔离。这一壮举是如何完成的？答案在于：向大脑组织供血的毛细血管的独特结构。与其他毛细血管的细胞不同，脑毛细血管的细胞形成连续的壁，阻止许多物质进入大脑。不间断的毛细血管壁为血脑屏障提供了基础，血脑屏障的存在在 20 世纪 60 年代首次被证实。通过将大脑与其他组织隔离开来，屏障发挥着至关重要的作用。然而，如果完全隔离，大脑就会因缺乏营养而死亡。幸运的是，在识别特定分子并将其带入大脑的运输系统的帮助下，必需营养素很容易穿过血脑屏障。最近关于血脑屏障的大部分工作，包括我们自己的工作，都集中在运输系统上。很明显，有几种不同类型的转运蛋白，每种转运蛋白都有特定的功能。运输系统不仅将营养物质带入大脑，还将多余的物质泵出，从而有助于维持恒定的
In human beings and other complex organisms, life itself depends on homeostasis, the maintenance of a constant internal milieu. Nowhere is this dependence more pronounced than in the brain. Elsewhere in the body the extracellular concentrations of hormones, amino acids and ions such as potassium undergo frequent small fluctuations, particularly after meals or bouts of exercise. If the brain were exposed to such fluctuations, the result might be uncontrolled nervous activity, because some hormones and amino acids serve as neurotransmit ters and potassium ion influences the threshold for the firing of nerve cells. Hence the brain must be kept rigor ously isolated from transient changes in the composition of the blood. How is this feat accomplished? The answer li.: s in the unique structure of the capillaries that supply blood to the tissues of the brain. The cells of brain capillaries, unlike those of other cap illaries, form a continuous wall that prevents many substances from enter ing the brain. The uninterrupted cap illary wall provides the basis of the blood-brain barrier, whose existence was first demonstrated conclusively in the 1960's. By cordoning off the brain from the other tissues, the barrier serves a critical function. Yet if the iso lation were complete, the brain would die for lack of nourishment. Fortu nately the essential nutrients traverse the blood-brain barrier easily, helped across by transport systems that recog nize specific molecules and carry them into the brain.Much of the recent work on the blood-brain barrier, including our own, has concentrated on the transport systems. It has become clear that there are several different types of trans porter, each of which has a specific function. The transport systems not only bring nutrients into the brain but also pump surplus substances out, thereby helping to maintain a constant