Horner Richard L, Liu Xia, Gill Harmeet, Nolan Philip, Liu Hattie, Sood Sandeep
Department of Medicine, University of Toronto, Toronto, Canada M5S 1A8.
J Appl Physiol (1985). 2002 Feb;92(2):878-87. doi: 10.1152/japplphysiol.00855.2001.
The effects of sleep on the ventilatory responses to hypercapnia have been well described in animals and in humans. In contrast, there is little information for genioglossus (GG) responses to a range of CO(2) stimuli across all sleep-wake states. Given the notion that sleep, especially rapid eye movement (REM) sleep, may cause greater suppression of muscles with both respiratory and nonrespiratory functions, this study tests the hypothesis that GG activity will be differentially affected by sleep-wake states with major suppression in REM sleep despite excitation by CO(2). Seven rats were chronically implanted with electroencephalogram, neck, GG, and diaphragm electrodes, and responses to 0, 1, 3, 5, 7, and 9% CO(2) were recorded. Diaphragm activity and respiratory rate increased with CO(2) (P < 0.001) across sleep-wake states with significant increases at 3-5% CO(2) compared with 0% CO(2) controls (P < 0.05). Phasic GG activity also increased in hypercapnia but required higher CO(2) (7-9%) for significant activation (P < 0.05). Further studies in 15 urethane-anesthetized rats with the vagi intact (n = 6) and cut (n = 9) showed that intact vagi delayed GG recruitment with hypercapnia but did not affect diaphragm responses. In the naturally sleeping rats, we also showed that GG activity was significantly reduced in non-REM and REM sleep (P < 0.04) and was almost abolished in REM even with stimulation by 9% CO(2) (decrease = 80.4% vs. wakefulness). Such major suppression of GG activity in REM, even with significant respiratory stimulation, may explain why obstructive apneas are more common in REM sleep.
睡眠对高碳酸血症通气反应的影响在动物和人类中已有详尽描述。相比之下，关于舌颏肌（GG）在所有睡眠-清醒状态下对一系列二氧化碳刺激的反应，相关信息却很少。鉴于睡眠，尤其是快速眼动（REM）睡眠，可能会对具有呼吸和非呼吸功能的肌肉产生更大程度的抑制这一观点，本研究检验了以下假设：尽管二氧化碳会刺激舌颏肌活动，但睡眠-清醒状态会对其产生不同影响，其中REM睡眠会对舌颏肌活动产生主要抑制作用。七只大鼠被长期植入脑电图、颈部、舌颏肌和膈肌电极，并记录对0%、1%、3%、5%、7%和9%二氧化碳的反应。在所有睡眠-清醒状态下，膈肌活动和呼吸频率随二氧化碳浓度升高而增加（P < 0.001），与0%二氧化碳对照组相比，在3%-5%二氧化碳时显著增加（P < 0.05）。在高碳酸血症状态下，舌颏肌的阶段性活动也会增加，但需要更高浓度的二氧化碳（7%-9%）才能产生显著激活（P < 0.05）。对另外15只完整迷走神经（n = 6）和切断迷走神经（n = 9）的乌拉坦麻醉大鼠进行的进一步研究表明，完整的迷走神经会使高碳酸血症时舌颏肌的募集延迟，但不影响膈肌反应。在自然睡眠的大鼠中，我们还发现，非快速眼动睡眠和快速眼动睡眠时舌颏肌活动显著降低（P < 0.04），即使受到9%二氧化碳刺激，快速眼动睡眠时舌颏肌活动也几乎完全消失（与清醒状态相比降低了80.4%）。即使在有显著呼吸刺激的情况下，快速眼动睡眠中舌颏肌活动仍受到如此主要的抑制，这可能解释了为什么阻塞性呼吸暂停在快速眼动睡眠中更为常见。
