Noguchi Tomohiro, Ikeda Yasutaka, Miyajima Mai, Yoshii Kiyonori
Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Fukuoka 808-0196, Japan.
Brain Res. 2003 Aug 29;982(2):241-59. doi: 10.1016/s0006-8993(03)03013-0.
Taste bud cells (TBCs) on soft palates differ from those on tongues in innervation and chemosensitivity. We investigated voltage-gated channels involved in the taste responses of TBCs on mouse soft palates under in-situ tight-seal voltage/current-clamp conditions. Under the cell-attached mode, TBCs spontaneously fired action currents, which were blocked by application of 1 microM TTX to TBC basolateral membranes. Firing frequencies increased in response to taste substances applied to TBC receptor membranes. Under the whole-cell clamp mode, as expected, TBCs produced various voltage-gated currents such as TTX-sensitive Na+ currents (INa), outward currents (Iout) including TEA-sensitive and insensitive currents, inward rectifier K+ currents (Iir), and Ca2+ currents including T-type, P/Q-type, and L-type Ca2+ currents. We classified TBCs into three types based on the magnitude of their voltage-gated Na+ currents and membrane capacitance. HEX type (60% of TBCs examined) was significantly larger in Na+ current magnitude and smaller in membrane capacitance than LEX type (23%). NEX type (17%) had no Na+ currents. HEX type was equally distributed within single taste buds, while LEX type was centrally distributed, and NEX type was peripherally distributed. There were correlations between these electrophysiological cell types and morphological cell types determined by three-dimensional reconstruction. The present results show that soft palate taste buds contain TBCs with different electrophysiological properties, and suggest that their co-operation is required in taste transduction.
软腭上的味蕾细胞（TBCs）在神经支配和化学敏感性方面与舌头上的味蕾细胞不同。我们在原位紧密密封电压/电流钳制条件下，研究了参与小鼠软腭TBCs味觉反应的电压门控通道。在细胞贴附模式下，TBCs自发产生动作电流，将1 microM的河豚毒素（TTX）应用于TBC基底外侧膜可阻断该电流。向TBC受体膜施加味觉物质时，放电频率增加。在全细胞钳制模式下，正如预期的那样，TBCs产生了各种电压门控电流，如TTX敏感的Na+电流（INa）、外向电流（Iout，包括TEA敏感和不敏感电流）、内向整流K+电流（Iir）以及包括T型、P/Q型和L型Ca2+电流在内的Ca2+电流。我们根据电压门控Na+电流的大小和膜电容将TBCs分为三种类型。与LEX型（23%）相比，HEX型（所检测TBCs的60%）的Na+电流幅度显著更大，膜电容更小。NEX型（17%）没有Na+电流。HEX型均匀分布在单个味蕾内，而LEX型集中分布，NEX型分布在周边。这些电生理细胞类型与通过三维重建确定的形态学细胞类型之间存在相关性。目前的结果表明，软腭味蕾包含具有不同电生理特性的TBCs，并表明味觉转导需要它们的协同作用。
