Human psychophysical studies of saltiness suppression by amiloride

Two studies were performed to assess the effects of amiloride on the saltiness of NaCl. In the first study, four highly trained subjects were asked to report the first appearance of saltiness as NaCl microdrops were rapidly applied to an increasing number of fungiform papillae along the front, dorsal surface of the tongue. For two subjects, amiloride, a sodium channel blocker, caused a large and significant increase in the number of papillae needed to report a salty taste. The other two subjects were unaffected, as measured by this procedure. In the second study, four different subjects were trained in the same procedure as in the previous study. For testing, however, they were stimulated on a fixed number of papillae, which was two times the number self-selected during training as sufficient for perception of saltiness with NaCl, and sourness with citric acid. They reported the quality of the experience as salty, sour, or neither, with and without amiloride treatment of the papillae set. Two of the four subjects had a loss of saltiness of NaCl, but not sourness of citric acid, when the papillae set was treated with amiloride.