IONIC MECHANISM OF WATER RECEPTORS IN THE LARYNGEAL MUCOSA OF THE RABBIT

抄録

The effects of various ions on water response was studied by recording unitary discharges in single superior laryngeal nerve fibers of the rabbit. The water response was strongly influenced by anions. The inorganic anions used were divided into two groups. One group consisted of anions which depress the water response (depressing anions), the depressing action sequence being SCN^->Br^->Cl^->I^->NO^-₃. Another one consisted of anions which facilitate the water response (facilitating anions), the facilitating action sequence being citrate>SO^2-₄>IO^-₃>F^->BrO^-₃>acetate. Physicochemically, facilitating anions belong to “the water structure-making ions” group;on the other hand, depressing anions belong to “the water structure-breaking ions” group. SO^2-₄weakened the depressing effect of Cl^-when the concentration of Cl^-was below 60mM, and enhanced it when the concentration was above 60mM.Na⁺and Li⁺had no appreciable effect on the water unit activity, but K⁺had a weakly stimulating effect. It is concluded that an outflux of anions through the membrane stimulates the water receptor while an influx of anions depresses it, and SO^2-₄facilitates Cl^-permeability. The mechanism of the facilitating effect of SO^2-₄on Cl^-permeation is discussed in terms of the interaction between the water structure surrounding the ions and the receptor membrane.