School of Human Kinetics, University of British Columbia, Vancouver, British Columbia, Canada.
J Appl Physiol (1985). 2010 Apr;108(4):906-12. doi: 10.1152/japplphysiol.01228.2009. Epub 2010 Feb 11.
Hypoxia may sensitize the carotid chemoreceptors, resulting in a sustained elevation of muscle sympathetic nerve activity (MSNA) that outlasts the hypoxic stimulus. To test this hypothesis, we determined the effect of carotid body inhibition on the sustained elevation of MSNA following isocapnic hypoxia in humans. Seven healthy subjects (5 male, 2 female) breathed 100% O(2) (hyperoxia) for 1 min before (2 interventions) and after (2-3 interventions) 20 min of isocapnic hypoxia (80% arterial oxyhemoglobin saturation). MSNA was continuously recorded from the common peroneal nerve with microneurography. There was no effect of hyperoxia on MSNA before exposure to isocapnic hypoxia. During the isocapnic hypoxia exposure, there was an increase in minute ventilation and heart rate that subsided once hypoxia was terminated. In contrast, there was an increase in MSNA burst frequency that persisted for approximately 25 min after cessation of the stimulus. Hyperoxia resulted in a transient reduction in MSNA burst frequency of 28% (P < 0.05), 15% (P < 0.05), and 9% (P > 0.05) in the three posthypoxia interventions, respectively. Our results suggest that input from the carotid chemoreceptors is obligatory for the sustained elevation of MSNA initiated by chemoreflex stimulation. We attribute the decrease in MSNA to a transient hyperoxia-induced attenuation of carotid chemoreceptor sensitivity.
低氧可能使颈动脉体感受器敏感，导致肌肉交感神经活动（MSNA）持续升高，超过低氧刺激的持续时间。为了验证这一假设，我们测定了颈动脉体抑制对人类等张低氧后 MSNA 持续升高的影响。7 名健康受试者（5 名男性，2 名女性）先吸入 100% O2（高氧）1 分钟，然后在等张低氧（动脉血氧饱和度 80%）前（2 次干预）和后（2-3 次干预）各进行 20 分钟。采用微神经电图法连续记录来自腓总神经的 MSNA。高氧对低氧前的 MSNA 没有影响。在等张低氧暴露期间，分钟通气量和心率增加，一旦低氧终止，这些参数即恢复正常。相反，MSNA 爆发频率增加，在刺激停止后持续约 25 分钟。高氧导致 MSNA 爆发频率分别短暂降低 28%（P < 0.05）、15%（P < 0.05）和 9%（P > 0.05），在三次低氧后干预中分别如此。我们的结果表明，颈动脉体感受器的传入对于化学感受器刺激引起的 MSNA 持续升高是必需的。我们将 MSNA 的降低归因于短暂的高氧诱导的颈动脉体敏感性减弱。
