Chang Hsiao-Sen, Lee Kun-Ze
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.
Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan.
J Appl Physiol (1985). 2020 May 1;128(5):1130-1145. doi: 10.1152/japplphysiol.00857.2019. Epub 2020 Mar 12.
This study was designed to investigate extrinsic tongue muscle activity in response to bronchopulmonary C-fiber activation following midcervical spinal contusion in the rat. Esophageal pressure and electromyogram of the extrinsic tongue muscles (genioglossus and hyoglossus) were monitored before and after inhalation of capsaicin (25 and 100 µg/mL) at the acute (3 days), subchronic (12-16 days), and chronic (52-65 days) injured stages following unilateral midcervical spinal contusion. Three days after injury, the preinspiratory burst amplitude of the extrinsic tongue muscle at baseline was significantly greater in midcervical spinal-contused animals than in sham animals. At this time, capsaicin induced a significant reduction in both preinspiratory and inspiratory activity of the extrinsic tongue muscle in sham but not contused animals at the acute stage. During the chronic injured stage, capsaicin at 100 µg/mL induced stronger suppression of preinspiratory genioglossus muscle activity in the contused animals than in sham animals. These results demonstrated that cervical spinal cord injury alters upper airway motor outputs and their reflex modulation by bronchopulmonary C-fibers. The compensatory increase in respiratory activity of the extrinsic tongue muscle early after cervical spinal cord injury may help to maintain upper airway patency. However, under the condition of chronic cervical spinal cord injury, the increased suppression of genioglossus muscle activity by bronchopulmonary C-fiber activation may increase the risk of airway obstruction following chronic cervical spinal cord injury. Tongue muscle activity plays an important role in the regulation of upper airway patency. This study aimed to investigate the respiratory activity of the extrinsic tongue muscle in response to capsaicin-induced bronchopulmonary C-fiber activation following cervical spinal cord contusion. Midcervical spinal-contused animals exhibited a greater baseline preinspiratory burst amplitude of the extrinsic tongue muscle and were resistant to inhaled capsaicin-induced reduction of respiratory tongue muscle activity at the acute injured stage. However, inhalation of capsaicin caused a more severe attenuation of preinspiratory activity of the extrinsic tongue muscle at the chronic injured stage. These results suggest that the upper airway may be predisposed to collapse in response to bronchopulmonary C-fiber activation following chronic cervical spinal cord injury.
本研究旨在调查大鼠颈髓中部挫伤后，支气管肺C纤维激活时舌外肌的活动情况。在单侧颈髓中部挫伤后的急性（3天）、亚慢性（12 - 16天）和慢性（52 - 65天）损伤阶段，吸入辣椒素（25和100μg/mL）前后，监测食管压力和舌外肌（颏舌肌和舌骨舌肌）的肌电图。损伤后3天，颈髓中部挫伤动物的舌外肌在基线时的吸气前爆发幅度显著大于假手术动物。此时，辣椒素使假手术动物而非急性期挫伤动物的舌外肌吸气前和吸气活动显著降低。在慢性损伤阶段，100μg/mL的辣椒素对挫伤动物吸气前颏舌肌活动的抑制作用比假手术动物更强。这些结果表明，颈髓损伤会改变上呼吸道运动输出及其受支气管肺C纤维的反射调节。颈髓损伤后早期舌外肌呼吸活动的代偿性增加可能有助于维持上呼吸道通畅。然而，在慢性颈髓损伤的情况下，支气管肺C纤维激活对颏舌肌活动的抑制作用增强可能会增加慢性颈髓损伤后气道阻塞的风险。舌肌活动在上呼吸道通畅的调节中起重要作用。本研究旨在调查颈髓挫伤后，舌外肌对辣椒素诱导的支气管肺C纤维激活的呼吸活动反应。颈髓中部挫伤动物的舌外肌在基线时吸气前爆发幅度更大，且在急性损伤阶段对吸入辣椒素诱导的舌肌呼吸活动降低具有抗性。然而，在慢性损伤阶段，吸入辣椒素导致舌外肌吸气前活动的衰减更严重。这些结果表明，慢性颈髓损伤后，上呼吸道可能更容易因支气管肺C纤维激活而塌陷。
