Walker J K, Jennings D B
Department of Physiology, Queen's University, Kingston, ON, Canada.
Can J Physiol Pharmacol. 1996 Nov;74(11):1258-64.
Angiotensin II (ANG II) stimulates ventilation (V), when ventilatory baroreceptor reflexes are taken into account, and arginine vasopressin (AVP) causes baroreflex inhibition of V in conscious and anesthetized dogs. To study mechanisms of hormonal modulation of V, a conscious rat model was investigated. V and metabolism were measured during steady-state intravenous infusions of ANG II and AVP in Sprague-Dawley rats (mean arterial pressure (MAP) increased 20 mmHg (1 mmHg = 133.3 Pa)). These data were compared with observations during equal pressor infusions of phenylephrine (PE), an agent classically used to study baroreceptor reflexes. V, respiratory frequency (f), and tidal volume (Vt) were maintained during the increased MAP associated with ANG II infusions, a response identical with that reported in conscious dogs. However, unlike dogs, AVP infusion did not depress V and metabolism in rats. PE in conscious rats caused an unexpected increase in Vt and V in association with increased metabolism. None of the pressor agents affected breath timing when the latter was binned by breath f. Since there was no obvious baroreflex inhibition of V with AVP and PE, potential stimulatory effects of ANG II on respiration could not be discerned. As well, the ventilatory baroreceptor pressure threshold may be higher or adaptation of the reflex may be faster in conscious rats than in dogs.
考虑到通气压力感受器反射时，血管紧张素II（ANG II）会刺激通气（V），而在清醒和麻醉的犬类中，精氨酸加压素（AVP）会导致压力反射对V的抑制。为了研究激素对V的调节机制，我们研究了一种清醒大鼠模型。在向斯普拉格-道利大鼠静脉内持续输注ANG II和AVP期间（平均动脉压（MAP）升高20 mmHg（1 mmHg = 133.3 Pa）），测量了V和代谢情况。这些数据与在等量输注去氧肾上腺素（PE）（一种经典用于研究压力感受器反射的药物）期间的观察结果进行了比较。在与ANG II输注相关的MAP升高期间，V、呼吸频率（f）和潮气量（Vt）保持稳定，这一反应与清醒犬类中报道的相同。然而，与犬类不同的是，AVP输注并未抑制大鼠的V和代谢。清醒大鼠输注PE会导致Vt和V意外增加，同时代谢也增加。当根据呼吸f对呼吸时间进行分类时，这些升压药物均未影响呼吸时间。由于AVP和PE均未对V产生明显的压力反射抑制，因此无法识别ANG II对呼吸的潜在刺激作用。此外，清醒大鼠的通气压力感受器压力阈值可能比犬类更高，或者反射的适应可能更快。
