Lee L Y, Pisarri T E
Department of Physiology, University of Kentucky Medical Center, Lexington, KY 40536-0298, USA.
Respir Physiol. 2001 Mar;125(1-2):47-65. doi: 10.1016/s0034-5687(00)00204-8.
Bronchopulmonary C-fiber afferents are characterized by their distinct sensitivity to chemical stimuli in the airways or pulmonary circulation. Responses evoked by activating these afferents are mediated by both central reflex pathways and by local or axon reflexes involving the release of tachykinins from sensory endings. Bronchopulmonary C-fiber stimulation reflexly reduces tidal volume and increases respiratory rate, constricts the airways, increases mucus secretion in the airways, and is associated with coughing. Cardiovascular effects include bradycardia, a fall in cardiac output, and bronchial vasodilation that increases airway blood flow despite systemic hypotension. In animals, C-fiber stimulation inhibits skeletal muscle activity, and in humans, is accompanied by burning and choking sensations in the throat and upper chest. Recent studies have identified additional physiologic and pharmacologic stimuli to these afferents, such as hydrogen ions, adenosine, reactive oxygen species, and hyperosmotic solutions. Furthermore, increasing evidence indicates that the excitability of these afferents is enhanced by the local release of certain autocoids (e.g. PGE2) during airway inflammation. These findings further indicate that vagal C-fiber endings in the lungs and airways play an important role in regulating the cardiopulmonary functions under both normal and abnormal physiologic conditions.
支气管肺C纤维传入神经的特点是对气道或肺循环中的化学刺激具有独特的敏感性。激活这些传入神经所引发的反应是由中枢反射通路以及涉及感觉末梢释放速激肽的局部或轴突反射介导的。刺激支气管肺C纤维会反射性地减少潮气量并增加呼吸频率，收缩气道，增加气道黏液分泌，并伴有咳嗽。心血管效应包括心动过缓、心输出量下降以及支气管血管舒张，尽管存在全身性低血压，但仍会增加气道血流量。在动物中，刺激C纤维会抑制骨骼肌活动，而在人类中，则会伴有喉咙和上胸部的烧灼感和窒息感。最近的研究已经确定了对这些传入神经的其他生理和药理刺激，如氢离子、腺苷、活性氧和高渗溶液。此外，越来越多的证据表明，在气道炎症期间，某些自体活性物质（如前列腺素E2）的局部释放会增强这些传入神经的兴奋性。这些发现进一步表明，肺和气道中的迷走神经C纤维末梢在正常和异常生理条件下调节心肺功能方面发挥着重要作用。
