Identification and Transduction Mechanisms in Chemoreceptor Cells

1. 利用犬的味觉系统研究了盐、甜物质和鲜味物质的味觉受体机制。结果表明，阿米洛利抑制了其对NaCl、KCI和NH_4Cl等盐的反应。这种对盐反应的抑制可以通过在盐受体位点上吸附氨酰化阳离子来解释。盐的存在大大增强了对糖的反应。这种增强可以用糖受体之间的协同性增加来解释。研究发现，犬的味觉系统对鲜味物质反应敏感。阿米洛利可抑制小鼠对味精（MSG）的反应，但对鸟苷酸二钠（GMP）或味精与GMP协同作用诱导的反应不受阿米洛利的抑制。这些结果表明，对味精的反应是由盐反应组成的，而对GMP单独或协同作用诱导的反应是由鲜味反应组成的。利用龟的嗅觉系统对嗅觉受体机制进行了研究。将交叉适应方法应用于龟的嗅觉系统，定量测定了龟对各种气味的辨别能力。该方法为研究嗅觉系统的构效关系开辟了道路。向龟嗅觉系统灌注无盐溶液后，其嗅觉系统对各种气味的反应没有改变，这表明位于嗅纤毛的阳离子通道对体内嗅觉系统没有贡献。发现由磷脂酰胆碱（PC）和磷脂酰丝氨酸（PS）组成的脂质体对各种气味有敏感反应。脂质体（PS/PC = 0.2）对乙酸戊酯的敏感性远高于海龟和青蛙的嗅觉系统。

1. Taste receptor mechanisms for salts, sweet substances and umami substances were investigated using the canine taste system. It was found that amiloride suppresses the responses to salts including NaCl, KCI and NH_4Cl. This suppression of the salt response was explained by adsorption of amiloride cation on the salt receptor sites. The responses to sugars were greatly enhanced by the presence of salts. The enhancement was explained by an increase in cooperativity between sugar receptors. It was found that canine taste system responds sensitively to umami substances. The response to monosodium glutamate (MSG) was suppressed by amiloride, but the response to disodium guanylate (GMP) or that induced by synergism between MSG and GMP was not suppressed by amiloride. These results suggested that the response to MSG is composed of salt response and the response to GMP alone or that induced by synergism is composed of umami response.2. Olfactory receptor mechanisms were investigated using the turtle olfactory system. The cross adaptation method was applied to the turtle olfactory system and discrimination of various odorants was quantitatively measured. This method opened the way to study the structure-activity relationship in olfactory system. Perfusion of the turtle olfactory system with salt free solution unchanged the olfactory responsed to various odorants, suggesting that cation channels located at olfactory cilia do not contribute to in vivo olfactory system. It was found that liposomes composed of phosphatidylcholine (PC) and phosphatidylserine (PS) respond sensitively to various odorants. The sensitivity of the liposomes (PS/PC = 0.2) to amyl acetate was much higher than that of the turtle or the frog olfactory system.