Cough reflex sensitization from esophagus and nose

Area of Science:

• Neuroscience
• Gastroenterology
• Otolaryngology

Background:

• Esophageal and nasal diseases are implicated in chronic cough, but their precise role is debated.
• Afferent C-fiber activation in the esophagus and nose enhances cough induced by irritants, not initiating it independently.
• This supports the hypothesis of C-fiber involvement in cough reflex hypersensitivity in conditions like gastroesophageal reflux disease (GERD) and chronic rhinitis.

Purpose of the Study:

• To investigate the contribution of esophageal and nasal C-fibers to cough reflex hypersensitivity.
• To explore the mechanisms of C-fiber activation in the esophagus and nose relevant to chronic cough.

Main Methods:

• Review of studies in animal models and humans examining C-fiber activation in esophageal and nasal mucosa.
• Analysis of C-fiber responsiveness to various stimuli, including acid and bile acids in the esophagus.
• Examination of sensory pathways and activators from the nose contributing to cough sensitization.

Main Results:

• Esophageal and nasal C-fibers do not initiate cough but enhance irritant-induced cough.
• Esophageal C-fibers are activated by acidic reflux (pH < 5) and weakly acidic reflux, including bile acids.
• Increased cough reflex sensitivity is observed in GERD and rhinitis patients, sometimes without overt cough.

Conclusions:

• Activation of esophageal and nasal C-fibers plays a significant role in cough reflex hypersensitivity associated with GERD and chronic rhinitis.
• Vagal jugular C-fibers are likely involved in esophageal cough sensitization.
• Additional factors may be necessary for chronic cough development in patients with underlying GERD or rhinitis.