The effect of amiloride analogs on taste responses in gerbil

Amiloride analogs that were designed to inhibit three types of Na+ transport systems (the epithelial Na+ channel, the Na+/H+ antiporter, and the Na+/Ca++ exchanger) were applied to the tongue of the gerbil to determine their effects of electrophysiological taste responses to NaCl, CaCl2, sucrose, and glutamic acid. The pattern of responses from the chorda tympani nerve indicates that the taste of NaCl is almost totally accounted for by the epithelial Na+ channel. Phenamil, an amiloride analog which specifically blocks the epithelial Na+ channel at low concentrations, suppressed the taste responses to 0.03 M NaCl by 97%. The pattern of responses also indicates that the Na+/H+ antiporter and the Na+/Ca2+ exchanger do not mediate salt taste in the gerbil. None of the amiloride analogs blocked taste responses to CaCl2, sucrose, or glutamic acid. It is concluded that the salty taste of NaCl in the gerbil is almost totally mediated by the epithelial Na+ channel, and the kinetics of this channel are identical to amiloride-sensitive sodium channels in other systems.