Kongo M, Yamamoto R, Kobayashi M, Nosaka S
Department of Physiology, Mie University School of Medicine, Japan.
Exp Physiol. 1999 Jan;84(1):47-56. doi: 10.1111/j.1469-445x.1999.tb00071.x.
It is known that arterial baroreflexes are suppressed in stressful conditions. The present study was designed to determine whether and how hypoxia affects arterial baroreflexes, especially the heart rate component, baroreflex vagal bradycardia. In chloralose-urethane-anaesthetized rats, baroreflex vagal bradycardia was evoked by electrical stimulation of the aortic depressor nerve, and the effect of 15 s inhalation of hypoxic gas (4% O2) was studied. Inhalation of hypoxic gas was found to inhibit baroreflex vagal bradycardia. The inhibition persisted after bilateral transection of the carotid sinus nerve. Cervical vagus nerves were cut bilaterally and their peripheral cut ends were stimulated to provoke vagal bradycardia of peripheral origin so as to determine whether hypoxia could inhibit vagal bradycardia by acting on a peripheral site. In contrast to baroreflex vagal bradycardia, the vagus-induced bradycardia was not affected by hypoxic gas inhalation. It is concluded that baroreflex vagal bradycardia is inhibited by hypoxia and the inhibition is largely mediated by its direct central action.
已知在应激条件下动脉压力反射会受到抑制。本研究旨在确定缺氧是否以及如何影响动脉压力反射，特别是心率成分，即压力反射性迷走性心动过缓。在氯醛糖 - 乌拉坦麻醉的大鼠中，通过电刺激主动脉减压神经诱发压力反射性迷走性心动过缓，并研究吸入15秒低氧气体（4%氧气）的效果。发现吸入低氧气体可抑制压力反射性迷走性心动过缓。双侧切断颈动脉窦神经后，这种抑制作用仍然存在。双侧切断颈迷走神经，并刺激其外周切断端以引发外周起源的迷走性心动过缓，从而确定缺氧是否可通过作用于外周部位来抑制迷走性心动过缓。与压力反射性迷走性心动过缓相反，迷走神经诱发的心动过缓不受吸入低氧气体的影响。得出的结论是，缺氧会抑制压力反射性迷走性心动过缓，且这种抑制主要由其直接的中枢作用介导。
