PRIMATE SENSE OF TASTE - BEHAVIORAL AND SINGLE CHORDA TYMPANI AND GLOSSOPHARYNGEAL NERVE-FIBER RECORDINGS IN THE RHESUS-MONKEY, MACACA-MULATTA

The responses of 51 chorda tympani propel (CT) and 33 glossopharyngeal (NG) neural taste units from the rhesus monkey (Macaca mulatta) were recorded during stimulation of either the anterior (CT) or posterior ( NG) part of the tongue with 26 stimuli thar taste salty, umami, sour, bitter. and sweet to humans. In the CT, hierarchical cluster analysis separated four major clusters. The N and S clusters were most populous , followed by the H cluster and a small Q cluster. NaCl, monosodium gl utamate (MSG). and MSG with guanosine 5'-monophosphate were the best s timuli in the N cluster. Amiloride suppressed responses to NaCl. KCl d id not stimulate fibers from this cluster. S cluster fibers were chara cterized by strong responses to all sweeteners. The H cluster responde d best to acids but also ro some of the sweeteners such as xylitol, fr uctose, and sucrose. Q fibers responded well to quinine hydrochloride (QHCl) and caffeine. but nor to denatonium benzoate. In the NG, hierar chical cluster analysis separated three major clusters. Q fibers forme d the largest cluster. QHCl, caffeine, and sucrose octa-acetate but no t denatonium benzoate elicited very strong responses in these fibers. S fibers formed a second cluster. Although most of the sweeteners stim ulated the S fibers, their responses were not so pronounced as in CT S fibers. The small M cluster was formed by fibers that responded best to MSG. They also responded to NaCl and acids. Two bottle preference t ests showed a positive relationship between a sweetener's ability to s timulate the taste fibers and the animals' consumption. Thus the most- liked sweeteners stimulated the S cluster fibers of CT best, whereas l ess-liked sweeteners such as D-phenylalanine elicited a response in Q fibers and sodium cyclamate stimulated N fibers. The results show that both CT and NG taste fibers of M. mulatta group according to the huma n concepts of taste qualities.