Taste Responses of Chorda Tympani Proper Nerve in the White-handed Gibbon (hylobates Lar)

Humans, chimpanzees and all Old World monkeys tested to date are able to taste the sweet compounds acesulfame-K, aspartame, D-tryptophan, sucrose, xylitol, monellin and thaumatin. In humans and chimpanzees, but not in rhesus macaques, gymnemic acid suppresses or abolishes the chorda tympani proper nerve response and the sweet taste of these compounds. This study examines the relationship between gymnemic acid and sweet taste responses in one species of the lesser apes, the white-handed gibbon (Hylobates lar). Recordings were made from the chorda tympani proper nerve during stimulation with these sweet compounds and some non-sweet taste stimuli before and after application of gymnemic acid to the tongue. Response amplitude and a number of other parameters were measured. Responses to the taste stimuli presented were similar to those found in other primate species. The effects of gymnemic acid on gibbons are intermediate between those of the greater apes and those of non-hominoid primates. As a tentative interpretation, we propose that sensitivity for gymnemic acid is a derived characteristic shared by gibbons and other hominoids, but not by other primates.