Figure 1

Primary sensory neurons of itch and cough. A. Itch is primarily sensed through the epithelium by unmyelinated C-fibers, whose cell bodies are in the dorsal root ganglion. Degranulation of mast cells release inflammatory mediators that can activate C-fibers, which secrete neuropeptides, such as Substance P. Secretion of Substance P results in inflammation and vasodilatation, which sensitizes nerves. B. Cough results from activation of myelinated cough receptors and unmyelinated C-fibers, whose cell bodies are in the jugular and nodose ganglia. Extensive C-fiber endings are found under the airway epithelium while cough receptors endings terminate in the mucosa between the epithelium and smooth muscle. Degranulated mast cells release mediators that activate C-fibers, causing release of Substance P. Substance P release results in inflammation, vasodilatation and sensitization of nerves.