在許多的研究中發現內毒素所引發呼吸性的反應中似乎與活化肺迷走感覺神經受器有關。但是,現今對於內毒素血症產生時,是否可影響呼吸系統中的肺迷走感覺神經受器的活性仍不清楚。本實驗是採用六十四隻麻醉、開胸、人工輔助呼吸的大白鼠為實驗動物,以單根神經記錄方式,記錄肺C纖維、快適應性受器、持續性的肺牽扯性受器和間歇性的肺牽扯性受器活性之變化。實驗結果顯示,以靜脈注射的方式給予內毒素(50毫克/公斤)後,在八個所記錄的肺C纖維中,有七個肺C纖維的放電頻率增加;另在八個所記錄的快適應性受器中,也皆可刺激全部的快適應性受器。至於在所記錄的八個持續性肺牽扯性受器中,內毒素可造成其中的四個受器的活性增加,但在另四個受器的活性卻不受明顯地影響;然而於八個間歇性的肺牽扯性受器反應中,發現內毒素則無法有效地影響其放電頻率。此外,內毒素刺激肺迷走感覺神經之開始時間約在給予內毒素後的三至十六分鐘,並且此刺激作用之時間仍持績至所記錄的九十分鐘。在內毒素刺激C纖維和快適應性受器的過程中,其神經活性的增加與呼吸週期的節律並不相關,是呈現一個不規律的放電狀態;但持續性肺牽扯性受器的刺激作用卻具有與呼吸週期相關的型態。再者,若給予生理食鹽水,在我們所觀察的九十分鐘內,皆不會明顯地影響所記錄的神經受器的活性。此外,給予內毒素可明顯地增加全肺阻力、降低動態之肺順應性及降低動脈血壓。根據以上的實驗結果,可知以靜脈注射的方式給予內毒素造成內毒素血症時可刺激肺迷走感覺神經受器,藉此神經受器活性的增加可扮演一偵測與調節肺功能的重要角色。
Several endotoxin-induced pulmonary responses are linked to the activation of lung vagal sensory receptors. However, the effects of circulatory endotoxin on lung vagal afferent activity are not clear. We recorded afferent activity arising from vagal pulmonary C fibers (CFs), rapidly adapting receptors (RARs), tonic pulmonary stretch receptors (T-PSRs), and phasic pulmonary stretch receptors (P-PSRs) in 64 anesthetized rats. Intravenous injection of endotoxin (50 mg/kg; lipopolysaccharide) stimulated 7 of the 8 CFs, 8 of the 8 RARs, and 4 of the 8 T-PSRs studied, while having no effect on the 8 P-PSRs tested. The stimulation started 3-16 min after endotoxin injection and lasted until the end of the 90-min observation period. The evoked discharge of either CFs or RARs was not in phase with the ventilatory cycle, whereas that of T-PSRs showed a respiratory modulation. Injection of a saline vehicle caused no significant change in the discharge of these receptors. Additionally, endotoxin significantly produced an increase in total lung resistance, and decreases in dynamic lung compliance and arterial blood pressure. Our results demonstrate that a majority of lung vagal sensory receptors are activated by intravenous endotoxin, and support the notion that these receptors may function as an important afferent system during endotoxemia.