Biophysics Program, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
J Cereb Blood Flow Metab. 2013 May;33(5):774-9. doi: 10.1038/jcbfm.2013.16. Epub 2013 Feb 13.
Effects of chronic hypoxia on hemodynamic response to sensory stimulation were investigated. Using laser-Doppler flowmetry, change in cerebral blood flow (CBF) was measured in awake mice, which were housed in a hypoxic chamber (8% O₂) for 1 month. The degree of increase in CBF evoked by sensory stimulation was gradually decreased over 1 month of chronic hypoxia. No significant reduction of increase in CBF induced by hypercapnia was observed during 1 month. Voltage-sensitive dye (VSD) imaging of the somatosensory cortex showed no significant decrease in neural activation over 1 month, indicating that the reduction of increase in CBF to sensory stimulation was not caused by cerebrovascular or neural dysfunction. The simulation study showed that, when effective diffusivity for oxygen in the capillary bed (D) value increases by chronic hypoxia due to an increase in capillary blood volume, an increase in the cerebral metabolic rate of oxygen utilization during neural activation can occur without any increase in CBF. Although previous study showed no direct effects of acute hypoxia on CBF response, our finding showed that hemodynamic response to neural activation could be modified in response to a change in their balance to energy demand using chronic hypoxia experiments.
研究了慢性缺氧对感觉刺激引起的血液动力学反应的影响。使用激光多普勒流量仪，在 1 个月的时间里，测量了居住在缺氧室（8% O₂）中的清醒小鼠的脑血流（CBF）变化。在慢性缺氧的 1 个月中，CBF 刺激引起的增加程度逐渐降低。在 1 个月期间，没有观察到由高碳酸血症引起的 CBF 增加的显著减少。体感皮层的电压敏感染料（VSD）成像显示，在 1 个月内，神经激活没有明显减少，这表明对感觉刺激的 CBF 增加减少不是由脑血管或神经功能障碍引起的。模拟研究表明，当由于毛细血管血液体积增加而导致毛细血管床中氧气的有效扩散系数（D）值在慢性缺氧下增加时，即使 CBF 没有增加，在神经激活期间，大脑的耗氧量也会增加。尽管先前的研究表明急性缺氧对 CBF 反应没有直接影响，但我们的发现表明，使用慢性缺氧实验，可以根据其与能量需求平衡的变化，对神经激活的血液动力学反应进行调节。
