title: Multiple receptors underlie glutamate taste responses in mice.
abstract: l-Glutamate is known to elicit a unique taste, umami, that is distinct from the tastes of sweet, salty, sour, and bitter. Recent molecular studies have identified several candidate receptors for umami in taste cells, such as the heterodimer T1R1/T1R3 and brain-expressed and taste-expressed type 1 and 4 metabotropic glutamate receptors (brain-mGluR1, brain-mGluR4, taste-mGluR1, and taste-mGluR4). However, the relative contributions of these receptors to umami taste reception remain to be elucidated. We critically discuss data from recent studies in which mouse taste cell, nerve fiber, and behavioral responses to umami stimuli were measured to evaluate whether receptors other than T1R1/T1R3 are involved in umami responses. We particularly emphasized studies of umami responses in T1R3 knockout (KO) mice and studies of potential effects of mGluR antagonists on taste responses. The results of these studies indicate the existence of substantial residual responses to umami compounds in the T1R3-KO model and a significant reduction of umami responsiveness after administration of mGluR antagonists. These findings thus provide evidence of the involvement of mGluRs in addition to T1R1/T1R3 in umami detection in mice and suggest that umami responses, at least in mice, may be mediated by multiple receptors.
authors: Kyushu University, Higashi-ku, Fukuoka, Japan.
authors: Keiko
authors: K
authors: Yasumatsu
authors: Nao
authors: N
authors: Horio
authors: Yoshihiro
authors: Y
authors: Murata
authors: Shinya
authors: S
authors: Shirosaki
authors: Tadahiro
authors: T
authors: Ohkuri
authors: Ryusuke
authors: R
authors: Yoshida
authors: Yuzo
authors: Y
authors: Ninomiya
mesh_terms: D000818:Animals; D002814:Chorda Tympani Nerve / Q000502:physiology; D005930:Glossopharyngeal Nerve / Q000502:physiology; D018698:Glutamic Acid; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000378:metabolism / Q000502:physiology; D055697:Taste Perception / Q000502:physiology*
chemical_list: D043562:Receptors, G-Protein-Coupled; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; C431926:taste receptors, type 1; D018698:Glutamic Acid; C108823:metabotropic glutamate receptor 4