The ionic mechanism underlying the receptor potential in frog taste cells induced by acid stimuli was studied with single microelectrodes by replacing superficial and interstitial fluids of the tongue with modified saline solutions. 2. The removal of Na+, Ca2+ and Cl- from the normal interstitial fluid did not affect the receptor potential induced by acid stimuli. Interstitial 100 mM-K+ saline did not affect the acid response. 3. The receptor potential was reduced greatly when Ca2+ was removed from the superficial saline, but was increased when the Ca2+ concentration was elevated. The removal of superficial Cl- did not affect the receptor potential. The receptor potential elicited by superficial Ca2+-free saline was partly due to Na+. Li+, K+, NH4+ or choline + substituted for Na+ in producing the receptor potential. The amiloride-sensitive Na+ channel on the receptor membrane did not contribute to the receptor potential. With pure water adaptation of the tongue surface, the mean magnitude of the acid response was 35% of the control. 4. The receptor potential was unaffected by superficial tetrodotoxin (TTX) but was blocked by superficial Ca2+ antagonists such as Co2+ and Cd2+. Sr2+ substituted for Ca2+ in generating the receptor potential. 5. The receptor potentials observed under various concentrations of superficial Ca2+ became smaller when Na+ was present in the superficial fluid, indicating a competition between Ca2+ and Na+. 6. It is concluded that a large portion of the receptor potential induced by acid stimuli is produced by cations passing through a tastant-gated Ca2+ channel on the taste receptor membrane. Both divalent (Ca2+, Sr2+) and monovalent (Na+, Li+, K+, NH4+, choline+) cations can pass through the Ca2+ channel. The other mechanism responsible for the remaining part of the receptor potential is discussed.
摘要
采用单微电极，通过用改良盐溶液替代蛙舌的表层和间质液，研究了酸刺激诱导的蛙味觉细胞感受器电位的离子机制。2. 从正常间质液中去除Na⁺、Ca²⁺和Cl⁻不影响酸刺激诱导的感受器电位。间质中100 mM - K⁺盐溶液不影响酸反应。3. 当从表层盐溶液中去除Ca²⁺时，感受器电位大幅降低，但当Ca²⁺浓度升高时，感受器电位增加。去除表层Cl⁻不影响感受器电位。表层无Ca²⁺盐溶液引发的感受器电位部分归因于Na⁺。Li⁺、K⁺、NH₄⁺或胆碱⁺替代Na⁺产生感受器电位。感受器膜上的氨氯地平敏感Na⁺通道对感受器电位无贡献。舌表面用纯水适应后，酸反应的平均幅度为对照的35%。4. 感受器电位不受表层河豚毒素（TTX）影响，但被表层Ca²⁺拮抗剂如Co²⁺和Cd²⁺阻断。Sr²⁺替代Ca²⁺产生感受器电位。5. 当表层流体中存在Na⁺时，在各种表层Ca²⁺浓度下观察到的感受器电位变小，表明Ca²⁺和Na⁺之间存在竞争。6. 得出结论，酸刺激诱导的感受器电位的很大一部分是由阳离子通过味觉感受器膜上的味觉剂门控Ca²⁺通道产生的。二价阳离子（Ca²⁺、Sr²⁺）和一价阳离子（Na⁺、Li⁺、K⁺、NH₄⁺、胆碱⁺）均可通过Ca²⁺通道。还讨论了负责感受器电位其余部分的其他机制。
