Pulmonary C-fiber activation enhances respiratory-related activities of the recurrent laryngeal nerve in rats

I. Jung Lu, Li Chi Ku, Jin Tun Lin, Kun Ze Lee, Ji Chuu Hwang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


The purpose of the current study was to characterize the response of the recurrent laryngeal nerve (RLN) to pulmonary C-fiber activation. Male rats of Wistar strain were anesthetized by urethane (1.2 g/kg, i.p.). Tracheostomy was performed. Catheter was inserted into the femoral artery and vein. Additional catheter was placed near the entrance of the right atrium via the right jugular vein. The animal was then paralyzed with gallamine triethiodide, ventilated and maintained at normocapnia in hyperoxia. Activities of the phrenic (PNA) and recurrent laryngeal nerves (RLNA) were monitored simultaneously. Two experimental protocols were completed. In the first experiment, various doses of capsaicin were delivered into the right atrium to activate pulmonary C-fibers with vagal intact. Low dose of capsaicin (1.25 μg/kg) produced apnea, a decrease in amplitude of PNA, an enhancement of RLNA during apnea and recovery from apnea, hypotension, and bradycardia. High dose of capsaicin (5 and 20 μg/kg) evoked the same tendency of response for both nerves and biphasic changes in blood pressure. Dose dependency was only seen in the period of apnea but not observable in nerve amplitudes. After bilateral vagotomy, low dose of capsaicin produced an increase in PNA without apnea, no significant change in RLNA, and hypertension. These results suggest that activation of vagal and nonvagal C-fibers could produce different reflex effects on cardiopulmonary functions. The reflex responses evoked by these two types of afferents might play defensive and protective roles in the airways and lungs.

Original languageEnglish
Pages (from-to)143-154
Number of pages12
JournalChinese Journal of Physiology
Issue number4
Publication statusPublished - 2002 Dec 31


  • Apnea
  • Bradycardia
  • Capsaicin
  • Hypertension
  • Hypotension
  • Phrenic nerve
  • Pulmonary C-fiber
  • Rat
  • Recurrent laryngeal nerve
  • Vagus nerve

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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