Enhancing effects of saccharin on gustatory responses to d-phenylalanine in monkey single chorda tympani fibers

Taste enhancing effects of sodium saccharin (Sac) on d-phenylalanine (d-Phe), first found in mice, were examined by comparing single fiber responses to various taste stimuli in the monkey chorda tympani nerve. Fifteen fibers sampled were divided into the following 5 groups according to their responsiveness to 5 prototypical taste stimuli: 8 sucrose-, 2 quinine-, 2 acid-, 2 NaC1- and one monosodium glutamate (MSG)-best fibers. Out of 8 sucrose-best fibers nor other fibers showed the enhancements. These results suggest that (1) the enhancement of d-Phe responses by Sac also occurs in the monkey peripheral taste system, and (2) there exist distinct receptor sites for d-Phe responsible for occurrence of the enhancement, and (3) taste cells possessing the d-Phe receptor site are innervated by a limited supopulation of sucrose-best fibers.