Tonosaki K, Funakoshi M
Department of Oral Physiology, School of Dentistry, Asahi University, Gifu, Japan.
Nature. 1988 Jan 28;331(6154):354-6. doi: 10.1038/331354a0.
Taste stimulus adsorption is believed to occur at the taste cell microvillous membrane. But due to technical difficulties of inserting glass electrodes 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. Here we report that cyclic AMP, cyclic GMP, EGTA or tetraethyl-ammonium 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.
味觉刺激吸附被认为发生在味觉细胞的微绒毛膜上。但由于将玻璃电极插入哺乳动物味觉细胞存在技术困难，关于味觉转导机制的了解甚少。可靠的细胞内记录对于确定味觉细胞的特性是必要的。此前已在小鼠身上实现了这一点，并在此进行报告。最近的实验表明，环核苷酸可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充当细胞内递质。但在哺乳动物味觉细胞的顶端膜发现的紧密连接不允许刺激物进入味蕾，这使得通过灌注化学溶液来改变味觉细胞的环境变得困难。在此我们报告，电泳注入小鼠味觉细胞的环磷酸腺苷（cAMP）、环磷酸鸟苷（cGMP）、乙二醇双四乙酸（EGTA）或四乙铵会诱导膜去极化并增加膜电阻。这些结果表明，由钙离子调节的环核苷酸酶级联反应可能以类似于视觉和嗅觉转导的方式介导控制味觉的钾离子通透性。
