SALT TASTE RESPONSES OF THE IXTH-NERVE IN SPRAGUE-DAWLEY RATS - LACK OF SENSITIVITY TO AMILORIDE

To explore characteristics of the salt taste function of taste recepto r cells located on the posterior tongue, we recorded electrophysiologi cal responses from the whole glossopharyngeal nerve in Sprague-Dawley (SD) rats. For all salts, relative response magnitudes increased with increased stimulus concentrations (0.2-2.0 M) of NH4+, K+, and Na+ sal ts. The order of effectiveness of stimulation for Cl- salts was NH4Cl > KCl > NaCl. For sodium salts, relative response magnitudes were anio n dependent. Sodium salts with small anions (NaCl, NaSCN, and NaNO3) h ad a much stronger stimulating effect than sodium salts with large ani on groups (Na2SO4, C2H3O2Na, and C6H11O7Na). The responses of the glos sopharyngeal nerve to the Na+ salts of NaCl, C2H3O2Na, and C6H11O7Na w ere not inhibited by the lingual application of the epithelial sodium transport blocker amiloride. This is in contrast to large amiloride se nsitivity of the chorda tympani nerve. Amiloride also failed to inhibi t the responses to K+ salts (KCl and KC2H3O2) and to NH4Cl. These resu lts demonstrate that taste receptors innervated by the glossopharyngea l nerve in SD rats lack amiloride sensitivity as observed in the gloss opharyngeal nerve of spontaneously hypertensive and Wistar-Kyoto rats. Furthermore, the difference between the small-anion group and the lar ge-anion group of Na+ salts in their effectiveness to produce response s in the glossopharyngeal nerve parallels the effects noted for the an ion dependence in the portion of the taste response resistant to amilo ride in the chorda tympani nerve. Sodium salts with the smaller anion produced the larger responses in both glossopharyngeal and chorda tymp ani nerves after amiloride. (C) 1998 Elsevier Science Inc.