Hellekant, G.; Geissmann, T.; Glaser, D. & Hard av Segerstad, C. 1990: Taste responses of chorda tympani proper nerve in the white-handed gibbon (Hylobates lar). In: ISOT X. Proceedings of the Tenth International Symposium on Olfaction and Taste, Oslo, Norway, July 16 - 20, 1989, p. 300, K.B. Døving (ed.), GCS (Graphic Communication System), Oslo. (Abstract only).

Taste responses of chorda tympani proper nerve in the white-handed gibbon (Hylobates lar)

G. Hellekant¹,T. Geissmann²; D. Glaser² & C. Hard av Segerstad<sup>1

1</sup>University of Wisconsin, Department of Veterinary Science, and Wisconsin Regional Primate Center Madison, WI 53706, USA
² Anthropological Institute, University Zürich-Irchel, Switzerland

Key words: Gibbon; taste; chorda tympani; sweet; gymnemic acid; thaumatin; monellin; Hylobates lar; primate evolution.

The gibbons (Hylobates lar; Fam. Hylobatidae) belong to the Hominoidea. This subfamily diverged from the common stem leading to the great apes and humans after the Old World monkeys (Cercopithecoidea) had diverged. Thus the gibbons are interpreted as being the most ancient surviving branch within the Hominoidea.

Man, chimpanzee and all Cercopithecoidea (monkey) tested so far have an ability to taste the sweet compounds: acesulfame-K, aspartame, D-tryptophane, sucrose, xylitol, monellin and thaumatin. In man and chimpanzee, but not in monkeys, gymnemic acid suppresses or abolishes the chorda tympani proper nerve response of these compounds. It is likely that at some ime during evolution, the great apes and man acquired sweet receptors sensitive to the effect of gymnemis acid which don't exist in monkey. In all the above primates, miraculin increases the taste nerve responses to acids which is perceived as an additional sweet taste to the sour one. The caused increase and sweetness are abolished by gymnemic acid.

The questions asked in this study are: how similar are the nerve responses to sweeteners in monkey, gibbon and chimpanzee, and what is the effect of gymnemic acid and miraculin in the gibbon?

Recordings were made from the chorda tympani nerve during stimulation with the sweet compounds mentioned above and NaCl, quinine and citric acid before and after gymnemic acid and miraculin. Besides recording the amplitudes of the summated response, other parameters of the summated response were measured.

The results showed that the responses to the above taste stimuli were similar to those found in other primate species. Gymnemic acid suppressed the response to sweeteners but less than in apes. Miraculin enhanced the response to acid. The enhancement could be suppressed by miraculin. Thus the effects in gibbons were intermediate between those in the greater apes and those in 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.