Substance P-immunoreactive nerves in endobronchial biopsies in cough-variant asthma and classic asthma

Respiration. 2003 Jan-Feb;70(1):49-53. doi: 10.1159/000068413.


Background: Unlike classic asthma, cough-variant asthma does not show any evidence of airway obstruction. The main symptom is a dry cough with little known pathophysiology. Hypersensitivity of the cough receptors in cough-variant asthma and an increase in the sensory nerve density of the airway epithelium in persistent dry cough patients have been reported. Therefore, it is possible that there is a higher sensory nerve density in cough-variant asthma patients than in classic asthma patients.

Objectives: This study was undertaken to compare the substance P (SP)-immunoreactive nerve density in mucosal biopsies of cough-variant asthma patients, classic asthma patients, and in control subjects.

Methods: Bronchoscopic biopsies were performed in 6 cough-variant asthma patients, 14 classic asthma patients, and 5 normal controls. The tissues obtained were stained immunohistochemically. The SP-immunoreactive nerve density was measured in the bronchial epithelium using a light microscope at 400 x magnification.

Results: SP- immunoreactive nerve density for the cough-variant asthma group was significantly higher than that of the classic asthma group (p = 0.001), and of the normal control group (p = 0.006).

Conclusions: It is possible that a sensory nerve abnormality within the airway may be related to hypersensitivity of the cough receptor, and that this may be one of the pathophysiologies of cough-variant asthma.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Asthma / classification
  • Asthma / metabolism*
  • Biopsy
  • Bronchi / innervation
  • Bronchi / metabolism*
  • Bronchoconstrictor Agents
  • Cough / metabolism*
  • Data Interpretation, Statistical
  • Female
  • Forced Expiratory Volume
  • Humans
  • Male
  • Methacholine Chloride
  • Microscopy
  • Middle Aged
  • Nerve Fibers / metabolism
  • Nerve Fibers / ultrastructure*
  • Severity of Illness Index
  • Substance P / metabolism*


  • Bronchoconstrictor Agents
  • Methacholine Chloride
  • Substance P