Schertel E R, Allen D A
Department of Veterinary Clinical Sciences, Ohio State University, Columbus 43210.
Am J Physiol. 1993 Dec;265(6 Pt 2):H1856-63. doi: 10.1152/ajpheart.1993.265.6.H1856.
We used an isolated perfused in situ left lung preparation to evaluate the hemodynamic response to specific pulmonary C-fiber stimulation with capsaicin in two groups of anesthetized dogs. In one group (n = 6), continuous administration of capsaicin at 5 micrograms.kg-1.min-1 into the isolated pulmonary circulation produced sustained (20 min) reflex decreases in mean arterial pressure, cardiac output, maximal left ventricular rate of pressure over time, and heart rate. These effects were abolished by vagotomy. In a second group (n = 5) of atropinized dogs, a mild hemorrhage was first performed in each dog during control conditions (capsaicin vehicle administration). The hemorrhage was performed by removing 10% of blood volume over 3 min and then replacing this blood 3 min later. After reinfusion and stabilization, the mild hemorrhage was repeated during continuous administration of capsaicin (6.0 +/- 1.0 microgram.kg-1.min-1) into the isolated pulmonary circulation. The decrease of mean arterial pressure in response to hemorrhage was significantly greater during capsaicin administration than during control conditions. Lung denervation prevented the effect of capsaicin administration on the response to hemorrhage. We concluded that continuous pulmonary C-fiber stimulation produces sustained cardiovascular depression and compromises the hemodynamic response to mild hemorrhage in dogs. This latter effect may represent a central alteration of baroreflex gain.
我们使用离体原位灌注左肺制备方法，来评估两组麻醉犬在给予辣椒素特异性刺激肺C纤维时的血流动力学反应。在一组（n = 6）中，以5微克·千克⁻¹·分钟⁻¹的剂量持续向离体肺循环中注入辣椒素，可使平均动脉压、心输出量、左心室压力随时间变化的最大速率以及心率持续（20分钟）反射性降低。这些效应可通过迷走神经切断术消除。在第二组（n = 5）已用阿托品处理的犬中，首先在对照条件下（给予辣椒素赋形剂）对每只犬进行轻度出血。出血方法是在3分钟内抽取10%的血容量，然后在3分钟后再输回这些血液。再灌注并稳定后，在向离体肺循环持续注入辣椒素（6.0±1.0微克·千克⁻¹·分钟⁻¹）的过程中重复进行轻度出血。与对照条件相比，在注入辣椒素期间，出血引起的平均动脉压降低幅度明显更大。肺去神经支配可防止注入辣椒素对出血反应产生影响。我们得出结论，持续刺激肺C纤维会导致持续的心血管抑制，并损害犬对轻度出血的血流动力学反应。后一种效应可能代表压力感受性反射增益的中枢性改变。
