McKay Leanne C, Janczewski Wiktor A, Feldman Jack L
Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1763, USA.
J Physiol. 2004 May 15;557(Pt 1):13-8. doi: 10.1113/jphysiol.2004.064006. Epub 2004 Mar 26.
The aim of this study was to determine if episodic hypoxia evokes persistent increases of genioglossus muscle (GG) activity, termed long-term facilitation (LTF), in neonatal rats in vivo. Experiments were performed on anaesthetized, spontaneously breathing, intubated neonatal rats (postnatal days (P) 3-7), divided into three groups. The first group (n= 8) was subjected to three 5-min periods of hypoxia (5% O(2)-95% N(2)) alternating with 5 min periods of room air. The second group (n= 8) was exposed to 15 min of continuous hypoxia. The third (n= 4) group was not exposed to hypoxia and served as a control. GG EMG activity and airflow were recorded before, during and for 60 min after episodic and continuous hypoxic exposure. During hypoxia, GG EMG burst amplitude and tidal volume (V(T)) significantly increased compared to baseline levels (episodic protocol: mean +/-S.E.M; 324 +/- 59% of control and 0.13 +/- 0.007 versus 0.09 +/- 0.005 ml, respectively; continuous protocol: 259 +/- 30% of control and 0.16 +/- 0.005 versus 0.09 +/- 0.007 ml, respectively; P < 0.05). After the episodic protocol, GG EMG burst amplitude transiently returned to baseline; over the next 60 min, burst amplitude progressively increased to levels significantly greater than baseline (238 +/- 40% at 60 min; P < 0.05), without any significant increase in V(T) and respiratory frequency (P> 0.05). After the continuous protocol, there was no lasting increase in GG EMG burst amplitude. We conclude that LTF of upper airway muscles is an adaptive respiratory behaviour present from birth.
本研究的目的是确定间歇性低氧是否会引起新生大鼠体内颏舌肌（GG）活动的持续增加，即长期易化（LTF）。实验在麻醉、自主呼吸、插管的新生大鼠（出生后第（P）3 - 7天）身上进行，分为三组。第一组（n = 8）经历三个5分钟的低氧期（5% O₂ - 95% N₂），期间与5分钟的室内空气交替。第二组（n = 8）暴露于15分钟的持续低氧环境。第三组（n = 4）不暴露于低氧环境，作为对照。在间歇性和持续性低氧暴露之前、期间以及之后60分钟记录GG肌电图（EMG）活动和气流。在低氧期间，与基线水平相比，GG EMG爆发幅度和潮气量（V(T)）显著增加（间歇性方案：平均值±标准误；分别为对照的324±59%和0.13±0.007与0.09±0.005 ml；持续性方案：分别为对照的259±30%和0.16±0.005与0.0
9±0.007 ml；P < 0.05）。间歇性方案后，GG EMG爆发幅度短暂恢复到基线；在接下来的60分钟内，爆发幅度逐渐增加到显著高于基线的水平（60分钟时为238±40%；P < 0.05），而V(T)和呼吸频率没有任何显著增加（P> 0.05）。持续性方案后，GG EMG爆发幅度没有持续增加。我们得出结论，上气道肌肉的LTF是一种出生时就存在的适应性呼吸行为。
