Pisarri T E, Kendrick J E
Am J Physiol. 1984 Oct;247(4 Pt 2):H623-30. doi: 10.1152/ajpheart.1984.247.4.H623.
The ability of the carotid baroreflex to produce cardiac slowing during arterial hypoxia was investigated in dogs anesthetized with morphine-chloralose. The heart rate response to baroreflex stimulation decreased by about 20% at an arterial O2 tension (PaO2) of 65-70 Torr and by over 60% at a PaO2 of 15-20 Torr. After the aortic nerves were cut bilaterally, baroreflex stimulation produced greater cardiac slowing (P less than 0.001) during arterial hypoxia (PaO2 20 Torr) than at the same PaO2 with intact aortic nerves. The systemic depressor response to baroreflex stimulation was reduced in a qualitatively similar manner but with greater variability. After atropine (0.2 mg/kg iv) or vagal transection the heart rate response to baroreflex stimulation during hypoxia was not suppressed from its control. Perfusion of the head with hypoxic blood in carotid-denervated animals also reduced the baroreflex bradycardia. The results suggest that the vagal component of the baroreflex bradycardia is suppressed during arterial hypoxia both by a reflex mediated by the aortic chemoreceptors and by a direct effect of hypoxia on the central nervous system.
在使用吗啡 - 氯醛糖麻醉的犬中，研究了颈动脉压力反射在动脉缺氧期间产生心率减慢的能力。在动脉血氧分压（PaO2）为65 - 70托时，压力反射刺激引起的心率反应降低约20%，而在PaO2为15 - 20托时降低超过60%。双侧切断主动脉神经后，在动脉缺氧（PaO2 20托）期间，压力反射刺激比主动脉神经完整时在相同PaO2下产生更大程度的心率减慢（P小于0.001）。压力反射刺激引起的全身降压反应以定性相似的方式降低，但变异性更大。静脉注射阿托品（0.2毫克/千克）或切断迷走神经后，缺氧期间压力反射刺激引起的心率反应未从对照水平受到抑制。在去颈动脉动物中用缺氧血液灌注头部也降低了压力反射性心动过缓。结果表明，在动脉缺氧期间，压力反射性心动过缓的迷走神经成分既受到主动脉化学感受器介导的反射抑制，也受到缺氧对中枢神经系统的直接作用抑制。
