Generation Mechanisms of Mammalian Taste Receptor Cell Responses.

本研究旨在阐明味觉转导的主要机制。味觉刺激吸附被认为发生在味觉细胞微绒毛膜上。但由于将玻璃电极植入哺乳动物味觉细胞的技术困难，人们对味觉传导的机制知之甚少。可靠的细胞内记录对于确定味觉细胞的特征是必要的。这是以前在鼠标中完成的，此处报告了这一点。最近的实验表明，环核苷酸可以作用于多种细胞的膜内表面，改变其离子通道活性，这些物质可能在味觉细胞中起到细胞内递质的作用。但哺乳动物味觉细胞顶膜上发现的紧密连接不允许刺激进入味蕾，因此很难通过向味觉细胞灌流化学溶液来改变味觉细胞的环境。我研究了将cAMP、c-GMP、TEA、EGTA、IP_3等化学物质电泳性注入小鼠味觉细胞，引起细胞膜去极化和膜电阻增加。这些结果表明，受钙离子调节的环核苷酸酶级联可能以类似于视觉和嗅觉转导的方式介导控制味觉的钾通透性。因此，除甜味外，味觉转导机制尚不清楚。最近，我得到的结果是苦味转导主要依赖于IP_3级联，而咸味转导与其他类型的次要信使级联密切相关。这些结果的一部分已经发表在一些报告中。

The purpose of this research is going to clarified the primary taste transduction mechanisms. Taste stimulus adsorption is believed to occur at the taste cell microvillous membrane. But due to technical difficulties of inserting glass electrode into the mammalian taste cell, little is known about the mechanisms of taste transduction. Reliable intracellular recordings are necessary to determine the characteristics of taste cells. This has been accomplished previously in the mouse and is reported here. Recent experiments indicated that cyclic nucleotides can act on the inner surface of the membranes of a variety of cells to alter their ion-channel activity, and these substances might act as intracellular transmitters in taste cells. But tight junctions found at the apical membrane of mammalian taste cells do not allow stimuli to enter the taste bud, making it difficult to alter the environment of the taste cell by perfusing with chemical solutions. I studied that cyclic-AMP, c-GMP, TEA, EGTA, IP_3, and other kind of chemical substances electrophoretically injected into the mouse taste cell induce membrane depolarization and increased membrane resistance. These results suggest that a cyclic nucleotide enzymatic cascade, modulated by calcium ions, may mediate the potassium permeability that controls taste , in a way analogous to visual and olfactory transduction. Therefore, the taste transduction mechanisms, except sweet, are not clarified yet. Recently, I have got the results that bitter transduction was mainly depended on the IP_3 cascade and salty taste transduction was strongly related to the other kind of secondary messenger cascade. The part of those results have been published in some reports.