Characterization of inwardly rectifying potassium currents from dissociated rat taste receptor cells.

Inwardly rectifying potassium currents were recorded from taste receptor cells dissociated from the rat tongue with the use of patch-clamp techniques in the whole cell configuration. These currents displayed strong inward rectification at potentials negative to the potassium reversal potential and little outward current at potentials positive to it. With elevations of external potassium concentration, the slope and chord conductance increased, activation shifted toward more depolarized potentials, and the reversal potential varied in a predicted Nernst relationship. These currents were insensitive to 4-aminopyridine and partially blocked by tetraethylammonium. Both barium and cesium gave more complete blocks with characteristic relief at more negative potentials. Inhibition with barium was more voltage sensitive than with cesium. These currents were unaffected by changes in external sodium. The high conductance at negative membrane potentials suggests these currents may contribute with other conductances to the resting potential of taste cells. They may also participate in yet unidentified processes of taste transduction, resulting in the early depolarization of the resting potential.