Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
J Appl Physiol (1985). 2011 May;110(5):1299-310. doi: 10.1152/japplphysiol.00055.2011. Epub 2011 Mar 3.
Acute intermittent hypoxia (AIH) elicits a form of respiratory plasticity known as long-term facilitation (LTF). Here, we tested four hypotheses in unanesthetized, spontaneously breathing rats using radiotelemetry for EEG and diaphragm electromyography (Dia EMG) activity: 1) AIH induces LTF in Dia EMG activity; 2) diaphragm LTF (Dia LTF) is more robust during sleep vs. wakefulness; 3) AIH (or repetitive AIH) disrupts natural sleep-wake architecture; and 4) preconditioning with daily AIH (dAIH) for 7 days enhances Dia LTF. Sleep-wake states and Dia EMG were monitored before (60 min), during, and after (60 min) AIH (10, 5-min hypoxic episodes, 5-min normoxic intervals; n = 9), time control (continuous normoxia, n = 8), and AIH following dAIH preconditioning for 7 days (n = 7). Dia EMG activities during quiet wakefulness (QW), rapid eye movement (REM), and non-REM (NREM) sleep were analyzed and normalized to pre-AIH values in the same state. During NREM sleep, diaphragm amplitude (25.1 ± 4.6%), frequency (16.4 ± 4.7%), and minute diaphragm activity (amplitude × frequency; 45.2 ± 6.6%) increased above baseline 0-60 min post-AIH (all P < 0.05). This Dia LTF was less robust during QW and insignificant during REM sleep. dAIH preconditioning had no effect on LTF (P > 0.05). We conclude that 1) AIH induces Dia LTF during NREM sleep and wakefulness; 2) Dia LTF is greater in NREM sleep vs. QW and is abolished during REM sleep; 3) AIH and repetitive AIH disrupt natural sleep patterns; and 4) Dia LTF is unaffected by dAIH. The capacity for plasticity in spinal pump muscles during sleep and wakefulness suggests an important role in the neural control of breathing.
急性间歇性低氧（AIH）引发了一种称为长期易化（LTF）的呼吸可塑性。在这里，我们使用无线电遥测技术测量脑电图（EEG）和膈肌肌电图（Dia EMG）活动，在未麻醉、自主呼吸的大鼠中测试了四个假设：1）AIH 诱导 Dia EMG 活动中的 LTF；2）与觉醒相比，睡眠时膈肌 LTF（Dia LTF）更强大；3）AIH（或重复 AIH）破坏自然睡眠-觉醒结构；4）7 天每日 AIH（dAIH）预处理增强 Dia LTF。在 AIH（10 次，5 分钟缺氧期，5 分钟常氧间隔；n = 9）、时间对照（连续常氧，n = 8）之前（60 分钟）、期间和之后（60 分钟）监测睡眠-觉醒状态和 Dia EMG，以及 AIH 后 7 天进行 dAIH 预处理（n = 7）。在安静觉醒（QW）、快速眼动（REM）和非快速眼动（NREM）睡眠期间分析并归一化 Dia EMG 活动与同一状态下的 AIH 前值。在 NREM 睡眠期间，膈肌幅度（25.1 ± 4.6%）、频率（16.4 ± 4.7%）和分钟膈肌活动（幅度×频率；45.2 ± 6.6%）在 AIH 后 0-60 分钟时高于基线（所有 P < 0.05）。这种 Dia LTF 在 QW 时不太强大，在 REM 睡眠时不明显。dAIH 预处理对 LTF 没有影响（P > 0.05）。我们得出结论，1）AIH 在 NREM 睡眠和觉醒期间诱导 Dia LTF；2）与 QW 相比，NREM 睡眠中的 Dia LTF 更大，在 REM 睡眠期间消失；3）AIH 和重复 AIH 破坏自然睡眠模式；4）dAIH 对 Dia LTF 没有影响。在睡眠和觉醒期间脊髓泵肌肉的可塑性能力表明其在呼吸的神经控制中具有重要作用。
