Table 1.

List of TRP family of receptors found in upper and lower airways and their role in cough and hypersensitivity

Receptor	Location expressed	Endogenous agonists	Exogenous agonists	Temperature
TRPA1	Spinal dorsal root ganglia, nasal trigeminal and vagal airway neurons	Bradykinin PGE2 PAR2 Acid	Allyl isothiocyanate Allicin Cannabinol Acrolein Cinnamaldehyde Curcumin Umbellulone	<17°C
TRPV1	Spinal dorsal root ganglia, nasal trigeminal and vagal airway neurons	Bradykinin PGE2 PAR2	Resiniferatoxin Capsaicin Vanillitoxins Citric Acid Anandamide	>43°C
TRPV3	Oral and nasal epithelium, skin keratinocytes	2-aminoethoxydiphenyl borate Farnesyl pyrophosphate	Camphor Carvacrol Eugenol Thymol Menthol	31–39°C
TRPV4	Smooth muscle, alveolar wall and septae, pulmonary vasculature, tracheobronchial epithelium, mononuclear cells, alveolar macrophages, and neutrophils	Acid PAR2	Citric Acid	27–35°C
TRPM8	Spinal dorsal root ganglia, trigeminal ganglia, nasal and bronchial epithelial cells		Menthol Eucalyptol Icilin	<15–28°C
TRPC6	Bronchial epithelial cells, alveolar macrophages and pulmonary vasculature	Reactive oxygen species Diacylglycerol	Hyperforin

PGE2, prostaglandin E2; PAR2, protease activated receptor 2.