Department of Biological Sciences, 1155 Union Circle #305220, University of North Texas, Denton 76203, USA.
Poult Sci. 2010 Jan;89(1):135-44. doi: 10.3382/ps.2009-00362.
Heart rate variability is a common feature of the vertebrate cardiovascular system and is a consequence of variable input from the sympathetic and parasympathetic branches of the autonomic nervous system. The aim of this study was to examine the role of the autonomic nervous system in regulating heart rate and heart rate variability in 1-d-old emu hatchlings in normoxia and during exposure to 10% O2. The role of the autonomic nervous system in controlling emu heart rate and its variability was examined by blocking the action of the cholinergic and adrenergic pathways by administration of atropine and propranolol. Heart rate of 1-d-old hatchlings exhibited a significant cholinergic tone of 60 +/- 22 beats per minute (bpm) and beta-adrenergic tone of 28 +/- 17 bpm. Cholinergic tone was unchanged during hypoxic exposure (63.5 +/- 17.7 bpm), but adrenergic tone doubled to 68 +/- 15 bpm. Initially, the majority of hatchlings exhibited high frequency oscillations with a spectral peak at 0.22 +/- 0.02 Hz, associated with respiratory sinus arrhythmia. Beta-adrenergic blockade had no effect on respiratory sinus arrhythmia or spectral power in high frequency (HF; 0.1 to 0.7 Hz), low frequency (LF; 0.01 to 0.1 Hz), or total frequency (TF) ranges. After cholinergic blockade, spectral power in HF, LF, and TF ranges and respiratory sinus arrhythmia were all abolished. Hypoxia did not initially alter spectral power in the HF, LF, or TF ranges. beta-Adrenergic blockade along with hypoxia produced a significant increase in LF oscillations. A distinct LF oscillation appeared in most birds exposed to hypoxia that was abolished by cholinergic blockade. We conclude that although both the sympathetic and parasympathetic system exert a tonic influence on heart rate, the majority of HF and TF heart rate variability is mediated by the parasympathetic system in the emu hatchling. The sympathetic system contributes to LF heart rate oscillations by suppressing the influence of the parasympathetic system on LF oscillations.
心率变异性是脊椎动物心血管系统的一个常见特征，是自主神经系统交感和副交感分支可变输入的结果。本研究的目的是检查自主神经系统在调节 1 日龄鸸鹋雏鸟心率和心率变异性中的作用，在常氧和 10%O2 暴露下。通过给予阿托品和普萘洛尔阻断胆碱能和肾上腺素能途径的作用，检查自主神经系统在控制鸸鹋心率及其变异性中的作用。1 日龄雏鸟的心率表现出显著的胆碱能张力 60 +/- 22 次/分钟（bpm）和β-肾上腺素能张力 28 +/- 17 bpm。在低氧暴露期间，胆碱能张力没有变化（63.5 +/- 17.7 bpm），但肾上腺素能张力增加了一倍，达到 68 +/- 15 bpm。最初，大多数雏鸟表现出高频振荡，其频谱峰值为 0.22 +/- 0.02 Hz，与呼吸窦性心律失常有关。β-肾上腺素能阻断对呼吸窦性心律失常或高频（HF；0.1 至 0.7 Hz）、低频（LF；0.01 至 0.1 Hz）或总频率（TF）范围内的频谱功率没有影响。在胆碱能阻断后，HF、LF 和 TF 范围内的频谱功率和呼吸窦性心律失常均被消除。低氧最初并未改变 HF、LF 或 TF 范围内的频谱功率。β-肾上腺素能阻断加上低氧导致 LF 振荡显著增加。大多数暴露于低氧的鸟类都出现了明显的 LF 振荡，这种振荡在胆碱能阻断后被消除。我们的结论是，尽管交感和副交感系统都对心率产生紧张性影响，但大多数 HF 和 TF 心率变异性是由鸸鹋雏鸟的副交感神经系统介导的。交感神经系统通过抑制副交感神经系统对 LF 振荡的影响，有助于 LF 心率振荡。
