PHYSICOCHEMICAL STUDIES OF TASTE RECEPTION .5. SUPPRESSIVE EFFECT OF SALTS ON SUGAR RESPONSE OF FROG

The taste responses of frog [Rana catesbeiana] to various kinds of sugars were measured quantitatively by use of the glossopharyngeal nerve activity under an appropriate condition where the water response was completely suppressed. The concentration dependences of response of frog tongue to D-fructose, D-glucose and sucrose were almost the same; D-galactose, elicited a much larger response in comparison with the other sugars in the whole range of concentrations examined. The sugar response was suppressed extensively by the presence of small amount of salts in the stimulating sugar solution. The suppressive effects of NaCl, KCl, MgCl2, MgSO4 and K4Fe(CN)6 were examined with a fixed concentration of sugar. The results obtained with these salts, added in various concentrations, fell on a single curve when the data were plotted against the ionic strength in the stimulation solution. The taste receptor potential for salts on acids may be attributable to a change in the phase boundary potential at the membrane-solution interface.