West N H, Burggren W W
Am J Physiol. 1984 Nov;247(5 Pt 2):R884-94. doi: 10.1152/ajpregu.1984.247.5.R884.
In the conscious, undisturbed toad, Bufo marinus, pulmonary arterial blood flow increased during periods of lung ventilation and decreased in intervening periods of pulmonary apnea. In unidirectionally ventilated, anesthetized toads, lung inflation produced by increasing the outflow resistance to pulmonary gas flow to 3 cmH2O caused a significant increase in pulmonary arterial blood flow and a significant decrease in cutaneous arterial blood flow. Changes in flow were associated with reciprocal changes in calculated vascular resistance. Mean pulmocutaneous pressure and cardiac frequency did not change significantly. Thus lung inflation (in the absence of changes in the composition of intrapulmonary gases) increased the proportion of total pulmocutaneous flow routed to the lungs and decreased the proportion directed to the skin. Unidirectional ventilation with air + 5% CO2 at constant lung volume produced a significant decrease in pulmonary arterial blood flow, an increase in calculated pulmonary arterial flow resistance, and a small increase in the flow to the cutaneous artery. Concomitant mild hypoxia potentiated the effects of pulmonary hypercapnia, although hypoxia alone was less effective than hypercapnia alone in decreasing pulmonary flow. Pulmonary arterial blood flow was decreased by infusion of acetylcholine into the pulmocutaneous artery, but epinephrine had no effect on either the pulmonary or cutaneous artery at doses below those that produced systemic effects. Atropine blocked all changes in pulmonary arterial blood flow. This and other evidence suggest that calculated arterial resistance changes are due to reflex changes in the tone of vascular smooth muscle. Intrapulmonary CO2-sensitive mechanoreceptors possess appropriate response characteristics to mediate the afferent limb of the reflex.
在清醒、未受干扰的海蟾蜍（Bufo marinus）中，肺通气期间肺动脉血流量增加，而在肺呼吸暂停的间歇期则减少。在单向通气、麻醉的蟾蜍中，通过将肺气体流出阻力增加到3 cmH₂O产生的肺膨胀，导致肺动脉血流量显著增加，皮肤动脉血流量显著减少。血流变化与计算出的血管阻力的相应变化相关。平均肺皮压力和心率没有显著变化。因此，肺膨胀（在肺内气体成分无变化的情况下）增加了流向肺部的总肺皮血流比例，减少了流向皮肤的比例。在肺容积恒定的情况下，用空气 + 5% CO₂进行单向通气，导致肺动脉血流量显著减少，计算出的肺动脉血流阻力增加，皮肤动脉血流略有增加。伴随的轻度低氧增强了肺高碳酸血症的影响，尽管单独的低氧在减少肺血流方面比单独的高碳酸血症效果差。向肺皮动脉注入乙酰胆碱可使肺动脉血流量减少，但肾上腺素在产生全身效应的剂量以下对肺动脉或皮肤动脉均无影响。阿托品阻断了肺动脉血流量的所有变化。这一证据及其他证据表明，计算出的动脉阻力变化是由于血管平滑肌张力的反射性变化所致。肺内对CO₂敏感的机械感受器具有适当的反应特性，可介导反射的传入支。
