Functional morphology and physiological properties of bronchopulmonary C-fiber afferents

Lu Yuan Lee, You Shuei Lin, Qihai Gu, Eleanor Chung, Chin Yin Ho

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


Nonmyelinated (C-) fibers represent the majority of vagal afferents innervating the airways and lung, and play an important role in regulating the respiratory and cardiovascular functions under both normal and abnormal physiologic conditions. Studies of the relationship between the conduction velocities of the vagal afferents and their sensitivities to capsaicin and other chemical irritants reveal that C-fibers are the primary type of chemosensitive afferents in the rat lung. Furthermore, a distinct sensitivity to capsaicin and a weak response to lung inflation are the defining characteristics of these afferents. In cultured rat nodose and jugular ganglion neurons, capsaicin-sensitive cells were identified by measurement of the capsaicin-evoked calcium transients using the Fura-2-based ratiometric imaging technique. The percentage of capsaicin-sensitive neurons gradually decreases as the cell diameter increases. However, the capsaicin-sensitive neurons cannot be precisely identified solely on the basis of the cell size. Anandamide, an endogenous cannabinoid released from leukocytes and epithelial cells, consistently evokes a stimulatory effect on pulmonary C-fiber endings by activating vanilloid receptor type 1 (VR1). The discharge pattern of pulmonary C-fibers evoked by anandamide closely resembles that produced by a much lower (∼1/600) dose of capsaicin in the same fibers. Whether anandamide acts as a potential endogenous ligand to VR1 at the C-fiber terminals is unclear, and the physiological role of VR1 in modulating the transduction properties of these afferents also remains to be determined.

Original languageEnglish
Pages (from-to)17-24
Number of pages8
JournalAnatomical Record - Part A Discoveries in Molecular, Cellular, and Evolutionary Biology
Issue number1
StatePublished - Jan 1 2003


  • Airway reflex
  • Anandamide
  • Calcium transient
  • Capsaicin
  • Inhaled irritant
  • Vagus
  • Vanilloid receptor

ASJC Scopus subject areas

  • Anatomy
  • Agricultural and Biological Sciences (miscellaneous)


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