The oral sensation of carbonated water: cross-desensitization by capsaicin and potentiation by amiloride.

The oral sensation elicited by carbonated water is reduced by capsaicin and by blockers of carbonic anhydrase. We have investigated the temporal profile of this sensation and its cross-desensitization by capsaicin. We additionally tested if the sensation is influenced by amiloride. Following pretreatment of half of the dorsal tongue with 33 p.p.m. capsaicin, carbonated water was flowed over the tongue bilaterally for 5, 15 or 60 s. Subjects then performed a two-alternative forced choice test by indicating which side of the tongue had a stronger sensation and separately rated the sensory intensity on each side. Capsaicin significantly reduced the intensity of sensation elicited by carbonated water, consistent with cross-desensitization. This effect was weaker at 60 s because of a significant decline (desensitization) in ratings of the intensity of carbonated water on both sides of the tongue. Pretreatment with amiloride resulted in a small but significant increase in the intensity of the sensation elicited by the 15 s carbonated water stimulus, suggesting an amiloride-sensitive transduction mechanism.