| Abstract: | Psychophysical measurements were made of the perceived intensityand quality of sensations of chemical irritation before andafter the tip of the tongue had been desensitized to capsaicin(10 ppm). The results of the first experiment showed that capsaicindesensitization tended to reduce the perceived intensity ofirritation produced by approximately equipotent concentrationsof capsaicin (3 ppm), ethanol (30%), cinnamic aldehyde (2.5%)and NaCl (5M) applied to the tongue on filter paper disks; however,the reduction in irritation was less for the latter three compoundsthan for capsaicin and failed to reach statistical significancefor ethanol. Ratings of sensation quality suggested that thefour irritants produced different quality ‘profiles’,and that ethanol and cinnamic aldehyde were characterized bysensations of numbness as well as by sensations of burning andstinging/pricking. Follow-up experiments in which subjects ratedthe perceived intensity of individual sensation qualities showedthat desensitization dramatically reduced the burning and stinging/prickingcomponents of irritation, but left the sensations of numbnessand chemogenic warmth unchanged. It is concluded that lingualchemesthetic sensations are multidimensional, and mediated byboth capsaicinsensitive and capsaicin-insensitive sensory pathways. |
