Ryan M L, Hedrick M S, Pizarro J, Bisgard G E
Department of Comparative Biosciences, University of Wisconsin, Madison 53706.
Respir Physiol. 1993 Apr;92(1):77-90. doi: 10.1016/0034-5687(93)90121-p.
Norepinephrine inhibits ventilation in awake goats under normoxic, resting conditions. This inhibition is carotid body (CB) mediated and may be due to stimulation of noradrenergic receptor on the CB. Cao et al. (FASEB J. A118, 1991) recently suggested that CB noradrenergic receptors may be down regulated following 24-36 hours of hypoxic exposure in cats. Our study was aimed at determining whether a change in noradrenergic receptor sensitivity during ventilatory acclimatization to hypoxia (VAH) was responsible for the increased sensitivity of the CB to hypoxia during prolonged exposure to hypoxia in goats. We tested this hypothesis using intracarotid infusions of norepinephrine (NE) (0.5, 1.0, 5.0 micrograms.kg-1.min-1) and dopamine (DA) (1.0 micrograms.kg-1.min-1) in awake goats under control normoxic conditions, during 4 h of isocapnic hypoxia, and upon return to normoxia. NE and DA (1.0 micrograms.kg-1.min-1) both inhibited control ventilation significantly during the intracarotid infusions (56% and 62% decreases, respectively). No significant differences were found between the pre- and post-hypoxic infusions of NE and DA in normoxia. During hypoxia, inhibition of VE during NE and DA infusions was attenuated relative to control. Time-dependent change of the NE response were not apparent during the acclimatization period suggesting that a decreased carotid body chemoreceptor sensitivity to NE and DA is not responsible for the increased drive to breathe characteristic of ventilatory acclimatization to hypoxia.
在常氧、静息状态下，去甲肾上腺素抑制清醒山羊的通气。这种抑制作用是由颈动脉体（CB）介导的，可能是由于刺激了CB上的去甲肾上腺素能受体。Cao等人（《美国实验生物学会联合会杂志》A118，1991年）最近指出，猫在低氧暴露24 - 36小时后，CB去甲肾上腺素能受体可能会下调。我们的研究旨在确定在对低氧通气适应（VAH）过程中，去甲肾上腺素能受体敏感性的变化是否是山羊在长期低氧暴露期间CB对低氧敏感性增加的原因。我们在清醒山羊处于对照常氧条件下、等碳酸血症性低氧4小时期间以及恢复到常氧后，通过颈内动脉输注去甲肾上腺素（NE）（0.5、1.0、5.0微克·千克⁻¹·分钟⁻¹）和多巴胺（DA）（1.0微克·千克⁻¹·分钟⁻¹）来验证这一假设。在颈内动脉输注期间，NE和DA（1.0微克·千克⁻¹·分钟⁻¹）均显著抑制对照通气（分别降低56%和62%）。在常氧状态下，低氧前后输注NE和DA没有发现显著差异。在低氧期间，与对照相比，NE和DA输注期间对VE的抑制作用减弱。在适应期内，NE反应的时间依赖性变化不明显，这表明颈动脉体化学感受器对NE和DA的敏感性降低不是低氧通气适应过程中呼吸驱动增加的特征的原因。
