Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence.
Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence.
复制标题
高碳酸血症期间的脑血管反应性通过增强的交感神经影响而重置。
DOI：
10.1152/japplphysiol.00802.2010
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Shi,Xiangrong
中科院分区：
文献类型：
--
作者：
Zhang,Peizhen;Huang,Guoyuan;Shi,Xiangrong
交感神经活动影响脑血流量，但交感神经活动增强是否会使脑血管反应性重置为高碳酸血症尚不清楚。本研究验证了高碳酸血症时脑血管舒张受下体负压（LBNP）刺激的交感神经兴奋抑制的假设。在9名健康志愿者[年龄25岁（SD 3）]中评估了静息时和LBNP期间呼吸诱导的呼气末CO2分压（PetCO 2）增加期间的脑血流动力学反应。脑血流动力学反应的变化，大脑中动脉（MCAV），经颅多普勒超声和局部脑组织氧合（ScO 2），采用近红外光谱。再呼吸期间PetCO 2值在静息时从41.9 mmHg增加到56.5 mmHg，在LBNP为−15 Torr时从40.7 mmHg增加到56.0 mmHg。然而，每单位PetCO 2增加的MCAV和ScO 2的增加率（即，MCAV/PetCO 2和ScO 2/PetCO 2的斜率分别由静息时的2.62 ± 0.16 cm·s-1·mmHg-1和0.89 ± 0.10%/mmHg降至LBNP时的1.68 ± 0.18 cm·s-1·mmHg-1和0.63 ± 0.07%/mmHg（P≤0.05）。总之，脑血管反应性对高碳酸血症的敏感性，在MCAV和ScO 2的增加率方面，LBNP刺激的交感神经兴奋降低。
Sympathetic nerve activity influences cerebral blood flow, but it is unknown whether augmented sympathetic nerve activity resets cerebral vasoreactivity to hypercapnia. This study tested the hypothesis that cerebral vasodilation during hypercapnia is restrained by lower-body negative pressure (LBNP)-stimulated sympathoexcitation. Cerebral hemodynamic responses were assessed in nine healthy volunteers [age 25 yr (SD 3)] during rebreathing-induced increases in partial pressure of end-tidal CO2(PetCO2) at rest and during LBNP. Cerebral hemodynamic responses were determined by changes in flow velocity of middle cerebral artery (MCAV) using transcranial Doppler sonography and in regional cerebral tissue oxygenation (ScO2) using near-infrared spectroscopy. PetCO2values during rebreathing were similarly increased from 41.9 to 56.5 mmHg at rest and from 40.7 to 56.0 mmHg during LBNP of −15 Torr. However, the rates of increases in MCAV and in ScO2per unit increase in PetCO2(i.e., the slopes of MCAV/PetCO2and ScO2/PetCO2) were significantly (P≤0.05) decreased from 2.62 ± 0.16 cm·s−1·mmHg−1and 0.89 ± 0.10%/mmHg at rest to 1.68 ± 0.18 cm·s−1·mmHg−1and 0.63 ± 0.07%/mmHg during LBNP. In conclusion, the sensitivity of cerebral vasoreactivity to hypercapnia, in terms of the rate of increases in MCAV and in ScO2, is diminished by LBNP-stimulated sympathoexcitation.