Stimulation of guinea-pig tracheal afferent fibres by non-isosmotic and low-chloride stimuli and the effect of frusemide

J Physiol. 1995 Jan 1;482 ( Pt 1)(Pt 1):179-87. doi: 10.1113/jphysiol.1995.sp020508.


1. Inhalation of low-chloride or non-isosmotic solutions evokes cough or reflex bronchoconstriction in humans that is inhibited by frusemide (furosemide), whilst capsaicin-evoked cough is unaffected. Here we have examined the responses of single vagal afferent fibres innervating the isolated guinea-pig trachea to these stimuli, and tested the effect of frusemide on fibre responses. 2. Both distilled water and hypertonic saline applied for 30 s onto identified receptive fields produced marked excitation of all A delta and C fibres tested. Isotonic glucose, a low-chloride solution, was a less potent stimulant and caused excitation in 37% of A delta fibres and 69% of C fibres. There was no difference in the distribution of low-chloride sensitive and insensitive receptive fields. 3. In the presence of frusemide, responses of A delta fibres to isotonic glucose were significantly inhibited to 34.2 +/- 6.2% of the pre-drug control level. However, frusemide was without effect either on responses of A delta fibres to distilled water or hypertonic saline, or on responses of C fibres to capsaicin. 4. These data support a role for tracheo-bronchial A delta and C fibres in airway reflexes evoked by hypotonic, hypertonic and low-chloride stimuli. The protective effect of frusemide against airway responses to low-chloride but not to non-isosmotic solutions may reflect an action on sensory nerve endings.

MeSH terms

  • Animals
  • Capsaicin / pharmacology
  • Chlorides / pharmacology*
  • Female
  • Furosemide / pharmacology*
  • Guinea Pigs
  • In Vitro Techniques
  • Male
  • Nerve Fibers / drug effects*
  • Nerve Fibers / physiology
  • Neurons, Afferent / drug effects*
  • Neurons, Afferent / physiology
  • Trachea / drug effects
  • Trachea / innervation*
  • Vagus Nerve / drug effects*
  • Vagus Nerve / physiology


  • Chlorides
  • Furosemide
  • Capsaicin