, Volume 105, Issue 3, pp 245-255

Amiloride-blockable sodium currents in isolated taste receptor cells

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Isolated taste receptor cells from the frog tongue were investigated under whole-cell patch-clamp conditions. With the cytosolic potential head at −80 mV, more than 50% of the cells had a stationary inward Na current of 10 to 700 pA in Ringer's solution. This current was in some cells partially, in others completely, blockable by low concentrations of amiloride. With 110mm Na in the external and 10mm Na in the internal solution, the inhibition constant of amiloride was (at −80 mV) near 0.3 μm. In some cells the amiloride-sensitive conductance was Na specific; in others it passed both Na and K. The Na/K selectivity (estimated from reversal potentials) varied between 1 and 100. The blockability bysmall concentrations of amiloride resembled that of channels found in some Na-absorbing epithelia, but the channels of taste cells showed a surprisingly large range of ionic specificities. Receptor cells, whichin situ express these channels in their apical membrane, may be competent to detect the taste quality “salty.” The same cells also express TTX-blockable voltage-gated Na channels.