Ndubuizu Obinna, LaManna Joseph C
Department of Physiology and Anatomy, Case Western Reserve University, Cleveland, Ohio 44106-4930, USA.
Antioxid Redox Signal. 2007 Aug;9(8):1207-19. doi: 10.1089/ars.2007.1634.
Brain function depends exquisitely on oxygen for energy metabolism. Measurements of brain tissue oxygen tension, by a variety of quantitative and qualitative techniques, going back for >50 years, have led to a number of significant conclusions. These conclusions have important consequences for understanding brain physiology as it is now being explored by techniques such as blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) and near-infrared spectroscopy (NIRS). It has been known for some time that most of the measured oxygen tensions are less than venous pO2 and are distributed in a spatially and temporally heterogeneous manner on a microregional scale. Although certain large-scale methods can provide reproducible average brain pO2 measurements, no useful concept of a characteristic oxygen tension or meaningful average value for brain tissue oxygen can be known on a microregional level. Only an oxygen field exists with large local gradients due to local tissue respiration, and the most useful way to express this is with a pO2 distribution curve or histogram. The neurons of the brain cortex normally exist in a low-oxygen environment and on activation are oxygenated by increases in local capillary blood flow that lead to increases in hemoglobin saturation and tissue oxygen.
脑功能对能量代谢所需的氧气极为依赖。五十多年来，通过各种定量和定性技术对脑组织氧张力进行测量，得出了一些重要结论。这些结论对于理解脑生理学具有重要意义，因为目前正通过诸如血氧水平依赖性功能磁共振成像（BOLD fMRI）和近红外光谱（NIRS）等技术来探索脑生理学。一段时间以来，人们已经知道，大多数测得的氧张力低于静脉血氧分压，并且在微观区域尺度上以空间和时间上的异质性方式分布。尽管某些大规模方法可以提供可重复的平均脑血氧分压测量值，但在微观区域水平上，对于脑组织氧的特征性氧张力或有意义的平均值尚无有用的概念。由于局部组织呼吸作用，仅存在具有大局部梯度的氧场，而表达此情况的最有用方法是使用血氧分压分布曲线或直方图。大脑皮层的神经元通常存在于低氧环境中，激活时通过局部毛细血管血流量增加而被氧化，这会导致血红蛋白饱和度和组织氧增加。
