Joint Study on Mechanisms of Umami Perception : Analyzes of the responses of taste cells to monosodium glutamate

味精有一种独特的味道，叫做鲜味。全细胞膜片钳记录从小鼠的vallate和foliate味蕾分离的味觉细胞表明，味精elflants几种不同类型的反应，这表明多种途径可能参与鲜味。我们还使用荧光染料和数字成像技术来测量MSG诱发的C3 H小鼠味觉细胞膜电位和细胞内钙的变化。在这项研究中，使用类似的成像技术记录B6小鼠的valate和foliate味觉细胞对MSG（10 mM）、代谢型受体激动剂L-AP 4（2-氨基-4-膦酰基丁酸酯）（1 mM）和离子型受体激动剂NMDA（1 mM）的反应。采用全细胞膜片钳技术研究了离体小鼠味觉细胞对味精和L-AP_4的反应。结果表明，MSG的感知通过代谢型谷氨酸受体4（mGluR 4）介导，降低膜电导， ...更多信息 d/或增加膜电导的另一种受体类型。用电压敏感染料di-8-ANNEPS和Ca^2+敏感染料fura-2对分离的味蕾细胞进行双重染色。由于中枢神经系统中的mGluR 4受体已被证明激活Gi，阻断K通道并使细胞去极化，我们研究了K通道阻断剂四乙基铵（TEA）对味觉细胞反应的影响。将TEA（10 mM）添加到浴溶液中导致约一半的味细胞中的膜去极化。此外，TEA显着减少了味觉细胞的数量，显示响应于MSG和L-AP 4的[Ca]i增加。与此相反，显示对NMDA的反应的味觉细胞的数量并没有减少TEA。在没有TEA的情况下，大约一半的细胞显示膜电位的变化时，用L-AP 4刺激。在TEA存在下，L-AP 4引起膜电位变化。这些结果与先前的膜片钳数据一致，表明MSG激活味觉细胞中的几种不同机制，包括由离子型和代谢型受体介导的过程。少

Monosodium glutamate (MSG) elicits a unique taste called umami. Whole-cell patch-clamp recordings from taste cells isolated from mouse vallate and foliate taste buds have indicated that MSG elicits several different types of responses, suggesting that multiple pathways may be involved in umami taste. We have also used fluorescent dyes and digital imaging techniques to measure MSG-evoked changes in membrane potential and intracellular calcium in taste cells from C3H mice. In this study, similar imaging techniques were used to record the responses of vallate and foliate taste cells from B6 mice to MSG (10 mM), the metabotropic receptor agonist, L-AP4 (2-amino-4-phosphonobutyrate)(1 mM) and the ionotropic receptor agonist, NMDA (1 mM). And we examined the responses of isolated mouse taste cells to MSG or L-AP4, by using whole-cell patch-clamp technique. The results suggest that MSG perception mediates via metabotropic glutamate receptor 4(mGluR 4) that decreases a membrane conductance, an … More d/or another receptor type that increases a membrane conductance. Cells in isolated taste buds were doubly stained with the voltage-sensitive dye, di-8-ANNEPS,and the Ca^<2+>-sensitive dye, fura-2. Since mGluR4 receptors in the CNS have been shown to activated Gi, blocked K channels and depolarize the cells, we examined the effect of the K channel blocker, tetraethyl ammonium (TEA), on taste cells responses. Addition of TEA (10 mM) to the bath solution resulted in membrane depolarization in about half of the taste cells. In addition, TEA markedly reduced the number of taste cells showing increases in [Ca]i in response to MSG and L-AP4. In contrast, the number of taste cells displaying responses to NMDA was not reduced by TEA.In the absence of TEA,approximately half of the cells displayd changes in membrane potential when stimulated with L-AP4. In the presence of TEA,membrane potential changes were elicited by L-AP4. These results are consistent with previous patch-clamp data suggesting that MSG activates several different mechanisms in taste cells, including processes mediated by ionotropic and metabotropic types of receptors. Less