Physiological evidence for ionotropic and metabotropic glutamate receptors in rat taste cells.
Physiological evidence for ionotropic and metabotropic glutamate receptors in rat taste cells.
复制标题
大鼠味觉细胞中离子型和代谢型谷氨酸受体的生理学证据。
DOI：
10.1152/jn.1999.82.5.2061
复制
发表时间：
1999
影响因子：
2.5
通讯作者：
Kinnamon,SC
中科院分区：
文献类型：
--
作者：
Lin,W;Kinnamon,SC
谷氨酸钠 (MSG) 会给人类带来一种独特的味道，称为鲜味。最近的分子研究表明，味觉细胞中存在与大脑中相似的谷氨酸受体，但它们在味觉传导中的确切作用仍有待阐明。我们使用千兆密封全细胞记录来检查味精和谷氨酸受体激动剂对大鼠蕈状乳头味觉细胞膜特性的影响。 MSG (1 mM) 在电压钳制在 -80 mV 的细胞中诱导三个子集的反应：保持电流减少（子集 I）、保持电流增加（子集 II）以及由保持电流增加和随后减少组成的双相反应（子集 III）。大多数子集 II 谷氨酸反应由离子型谷氨酸受体 (iGluR) 激动剂 N-甲基-d-天冬氨酸 (NMDA) 模拟。甘氨酸增强电流，并被 NMDA 受体拮抗剂 (-)-2-氨基-5-膦基戊酸 (AP5) 抑制。 III 类代谢型谷氨酸受体 (mGluR) 激动剂 2-氨基-4-磷酸丁酸 (l-AP4) 通常模仿 I 类谷氨酸反应。这种超极化反应被 mGluR 拮抗剂 (RS)-α-环丙基-4-膦酰基苯基甘氨酸 (CPPG) 和 8-溴-cAMP 抑制，表明 cAMP 在转导途径中发挥作用。在一小部分味觉细胞中，l-AP4 引起保持电流增加，导致味觉细胞在电流钳下去极化。综上所述，我们的结果表明味觉受体细胞中存在 NMDA 样受体和至少两种类型的 III 族 mGluR，并且这些可能被味精共同激活。需要进一步的研究来确定哪些受体位于顶膜上以及它们如何影响鲜味。
Monosodium glutamate (MSG) elicits a unique taste in humans called umami. Recent molecular studies suggest that glutamate receptors similar to those in brain are present in taste cells, but their precise role in taste transduction remains to be elucidated. We used giga-seal whole cell recording to examine the effects of MSG and glutamate receptor agonists on membrane properties of taste cells from rat fungiform papillae. MSG (1 mM) induced three subsets of responses in cells voltage-clamped at −80 mV: a decrease in holding current (subset I), an increase in holding current (subset II), and a biphasic response consisting of an increase, followed by a decrease in holding current (subset III). Most subset II glutamate responses were mimicked by the ionotropic glutamate receptor (iGluR) agonistN-methyl-d-aspartate (NMDA). The current was potentiated by glycine and was suppressed by the NMDA receptor antagonistd(−)-2-amino-5-phosphonopentanoic acid (AP5). The group III metabotropic glutamate receptor (mGluR) agonistl-2-amino-4-phosphonobutyric acid (l-AP4) usually mimicked the subset I glutamate response. This hyperpolarizing response was suppressed by the mGluR antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG) and by 8-bromo-cAMP, suggesting a role for cAMP in the transduction pathway. In a small subset of taste cells,l-AP4 elicited anincreasein holding current, resulting in taste cell depolarization under current clamp. Taken together, our results suggest that NMDA-like receptors and at least two types of group III mGluRs are present in taste receptor cells, and these may be coactivated by MSG. Further studies are required to determine which receptors are located on the apical membrane and how they contribute to the umami taste.