Physicochemical Study of Receptive Mechanism of Laryngeal Water Fibers in the Rabbit

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Abstract
The effects of various cations on the water unit activity were studied by recording unitary discharges in the superior laryngeal nerve fibers of the rabbit. Chloride salts of Li+, Na+, K+, Cs+ depressed the water response, while sulfate salts of Li+, Na+, NH4+, K+ facilitated it. Cations were less effective in stimulating action than anions. The depression of the water response in the laryngeal nerve was apparently caused by permeation of the stimulating anions through the receptor membrane and/or by destruction of the water structure on the membrane surface induced by adsorbed anions (Shingai, 1977). To differentiate these 2 possible actions of anions, the effects of benzenesulfonate and trichloroacetate were examined, because these anions were expected to be impermeant through the receptor membrane and to have a water structure-breaking effect. These anions showed no effect on the water response in concentrations below 320 mM. Measurements of the viscosity and the density of the electrolyte solutions showed that benzenesulfonate had a strong water structure-breaking effect. Impermeant anions having water structure-breaking actions perhaps do not influence the excitability of the water receptor and the depression of the water response by anions in the stimulating solution is apparently caused by a hyperpolarization generated by permeation of the anions through the receptor membrane.