Stimulation of Bitterness by Capsaicin and Menthol: Differences Between Lingual Areas Innervated by the Glossopharyngeal and Chorda Tympani Nerves

B. G. Green
2003 Chemical Senses  
Capsaicin is viewed as a purely chemesthetic stimulus that selectively stimulates the somatosensory system. Here we show that when applied to small areas of the tongue, capsaicin can produce a bitter taste as well as sensory irritation. In experiment 1, individuals were screened for the ability to perceive bitterness from capsaicin on the circumvallate papillae. Fifteen of 25 subjects who reported at least weak bitterness rated the intensity of taste, irritation and coolness produced by 100-320
more » ... produced by 100-320 µM capsaicin and 100-320 mM menthol applied via cotton swabs to the tip (fungiform region), the posterior edge (foliate region), and the dorsal posterior surface (circumvallate region) of the tongue. Sucrose, citric acid, sodium chloride and quinine hydrochloride were applied to the same areas to assess tastes responsiveness. On average, capsaicin and menthol produced 'moderate' bitterness (and no other significant taste qualities) in the circumvallate region, and weaker bitterness on the side and tip of the tongue. Sensory irritation from capsaicin was rated significantly higher at the tongue tip, whereas menthol coolness was rated higher in the circumvallate region. In experiment 2 we applied sucrose and quinine hydrochloride together with capsaicin to investigate the effects other taste stimuli might have on capsaicin's reported bitterness. 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doi:10.1093/chemse/28.1.45 pmid:12502523 fatcat:nrag32mhifcsjkgfjxzvzps6zq