STUDIES ON THE GUSTATORY SIGNAL TRANSDUCTION MECHANISMS OF MOUSE TASTE CELLS USING CONGENIC CELL LINE

众所周知，对盐刺激的味觉反应代表了一种品系差异。例如，C57BL/6菌株的盐敏反应表现出较强的阿米洛利敏感性，而BALB/c菌株的盐敏反应表现出较强的敏感性。我们试图检测从这两个菌株获得的味觉细胞和来自BALB/c菌株的同源菌株之间的味觉反应的差异。我们开发了一种方法，利用膜片钳技术，从嵌入味蕾中的未分离的味觉细胞中获得味觉反应，以保持这些极性。这种方法使我们能够仅对根尖膜进行局部刺激。结果如下：(1)阿米洛利敏感成分和非敏感成分均参与小鼠味觉细胞的盐反应。(2)盐反应可分为三种类型：(A)类型I包括阿米洛利敏感和不敏感成分，(B)类型II仅涉及阿米洛利敏感成分，(C)类型III仅涉及阿米洛利不敏感成分。由于已知BALB/c小鼠对氯化钠的厌恶阈值高于C57BL/6，阿米洛利不敏感的通路可能与不同于阿米洛利敏感通路的味觉传导通路有关。甜味信号转导机制之一K~+通道的抑制参与了阿米洛利不敏感通路的研究，支持这一假说。对于甜味，到目前为止，我们发现很少有味觉细胞对D-苯丙氨酸(D-Phe)做出反应。在这类味觉细胞中，5‘-GMP和糖精都增强了对D-Phe的反应。

The taste responses to salt-stimuli are known to represent a strain-differences. For example, the salt response of C57BL/6 strain indicates strong amiloride sensitivity, but that of BALB/c does not. we attempted to examine differences of the taste responses among taste cells obtained from these two strains and a congenic strain derived from BALB/c strain. We developed a method to obtain taste responses from non-dessociated taste cells, which are embedded in the taste bud so as to maintain those polarity, using patch clamp technique. This method enable us to perform the localized stimulation to the apical membrane alone. The results is as follows :(1) Both amiloride-sensitive and -insensitive components are involved in the salt responses of the mouse taste cells. The suppression of K^+ channels was suggested to be one of amiloride-insensitive components.(2) The salt responses were categorized into three types :(a) Type I consisted of both amiloride-sensitive and -insensitive components ;(b) Type II involved amiloride-sensitive component alone ;(c) Type III involved amiloride-insensitive component alone. Since the higher aversion threshold to NaCl was known to be observed in BALB/c mouse than in C57BL/6, the amiloride-insensitive pathway may relate to the transduction pathway for a different quality of taste from that the amiloride-sensitive pathway does. An involvement of the suppression of K^+ channels, which is one of the sweet taste transduction mechanisms, in the amiloride-insensitive pathway supports this hypothesis. For sweet taste, we have found few number of taste cells responded to D-phenylalanine (D-Phe) so far. In such taste cells responded to D-Phe, both 5'-GMP and saccharin enhanced the response to D-Phe.