title: Discrimination of taste qualities among mouse fungiform taste bud cells.
abstract: Multiple lines of evidence from molecular studies indicate that individual taste qualities are encoded by distinct taste receptor cells. In contrast, many physiological studies have found that a significant proportion of taste cells respond to multiple taste qualities. To reconcile this apparent discrepancy and to identify taste cells that underlie each taste quality, we investigated taste responses of individual mouse fungiform taste cells that express gustducin or GAD67, markers for specific types of taste cells. Type II taste cells respond to sweet, bitter or umami tastants, express taste receptors, gustducin and other transduction components. Type III cells possess putative sour taste receptors, and have well elaborated conventional synapses. Consistent with these findings we found that gustducin-expressing Type II taste cells responded best to sweet (25/49), bitter (20/49) or umami (4/49) stimuli, while all GAD67 (Type III) taste cells examined (44/44) responded to sour stimuli and a portion of them showed multiple taste sensitivities, suggesting discrimination of each taste quality among taste bud cells. These results were largely consistent with those previously reported with circumvallate papillae taste cells. Bitter-best taste cells responded to multiple bitter compounds such as quinine, denatonium and cyclohexamide. Three sour compounds, HCl, acetic acid and citric acid, elicited responses in sour-best taste cells. These results suggest that taste cells may be capable of recognizing multiple taste compounds that elicit similar taste sensation. We did not find any NaCl-best cells among the gustducin and GAD67 taste cells, raising the possibility that salt sensitive taste cells comprise a different population.
authors.affiliation: Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Yoshida
authors.forename: Aya
authors.initials: A
authors.lastname: Miyauchi
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yasuo
authors.forename: Masafumi
authors.initials: M
authors.lastname: Jyotaki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Murata
authors.forename: Keiko
authors.initials: K
authors.lastname: Yasumatsu
authors.forename: Noriatsu
authors.initials: N
authors.lastname: Shigemura
authors.forename: Yuchio
authors.initials: Y
authors.lastname: Yanagawa
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Obata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueno
authors.forename: Robert F
authors.initials: RF
authors.lastname: Margolskee
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Ninomiya
mesh_terms: D000818:Animals; D004056:Differential Threshold / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D012684:Sensory Thresholds / Q000502:physiology*; D013649:Taste; D013650:Taste Buds / Q000166:cytology* / Q000502:physiology*; D055697:Taste Perception / Q000502:physiology*