Sensory neurophysiology of the cough reflex.

The epithelium of the larynx, trachea, and larger bronchi contains sensory nerves that are responsible for cough. Their two main categories are rapidly adapting receptors (RARs) and C fiber receptors. Both types respond to a wide variety of mechanical and chemical irritants. The RARs are the main sensory complex responsible for cough. C fiber receptors cause neurogenic inflammation by the release of tachykinins such as substance P. The reflex action of C fiber receptors seems to be inhibition of cough. However, the released tachykinins can stimulate RARs and promote or enhance the cough response. The strength and pattern of cough depends on the sites of the airway that are stimulated and the local and central reflex interactions of the RARs and C fiber receptors. Tachykinins seem to be involved in cough, but their role needs further study.