Sweet Taste Responses of Mouse Chorda Tympani Neurons: Existence of Gurmarin-Sensitive and -Insensitive Receptor Components

1 Department of Oral Physiology, Asahi University School of Dentistry, Gifu 501-0296; and 2 Department of Physiology, Tottori University School of Medicine, Yonago 683-0826, Japan Ninomiya, Yuzo, Toshiaki Imoto, and Tadataka Sugimura. Sweet Taste Responses of Mouse Chorda Tympani Neurons: Existence of Gurmarin-Sensitive and -Insensitive Receptor Components. J. Neurophysiol. 81: 3087-3091, 1999. Sweet taste responses of mouse chorda tympani neurons: existence of gurmarin-sensitive and -insensitive receptor components. Inhibitory effects of gurmarin (gur) on responses to sucrose and other sweeteners of single fibers of the chorda tympani nerve in C57BL mice were examined. Of 30 single fibers that strongly responded to 0.5 M sucrose but were not or to lesser extent responsive to 0.1 M NaCl, 0.01 M HCl, and 0.02 M quinine HCl (sucrose-best fibers), 16 fibers showed large suppression of responses to sucrose and other sweeteners by lingual treatment with 4.8 µM (~20 µg/ml) gur (suppressed to 4-52% of control: gur-sensitive fibers), whereas the remaining 14 fibers showed no such gur inhibition (77-106% of control: gur-insensitive fibers). In gur-sensitive fibers, responses to sucrose inhibited by gur recovered to ~70% of control responses after rinsing the tongue with 15 mM -cyclodextrin and were almost abolished by further treatment with 2% pronase. In gur-insensitive fibers, sucrose responses were not inhibited by gur, but were largely suppressed by pronase. These results suggest existence of two different receptor components for sweeteners with different susceptibilities to gur in mouse taste cells, one gur sensitive and the other gur insensitive. Taste cells possessing each component may be specifically innervated by a particular type of chorda tympani neurons.