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 r esponses to various taste stimuli in the monkey chorda tympani nerve. Fifteen fibers sampled were divided into the following 5 groups accord ing to their responsiveness to 5 prototypical taste stimuli; 8 sucrose -, 2 quinine-, 2 acid-, 2 NaCl- and one monosodium glutamate (MSG)-bes t fibers. Out of 8 sucrose-best fibers, 5 fibers showed enhancement of D-Phe responses after the stimulation with Sac, but neither the remai ning 3 sucrose-best fibers nor other fibers showed the enhancement. Th ese results suggest that (1) the enhancement of D-Phe responses by Sac also occurs in the monkey peripheral taste system, and (2) there exis t distinct receptor sites for D-Phe responsible for occurrence of the enhancement, and (3) taste cells possessing the D-Phe receptor site ar e innervated by a limited subpopulation of sucrose-best fibers.