Inactivating and non-inactivating potassium currents in isolated inner hair cells from guinea pig cochlea

Using conventional whole-cell voltage-clamp recordings, we examined the 4-aminopyridine (4-AP)- and tetraethylammonium (TEA)-sensitive K(+) currents in the cochlear inner hair cells (IHCs) of guinea pigs. 4-AP-sensitive currents were activated slowly and sustained the same current level, whereas TEA-sensitive currents were activated rapidly, followed by inactivation. The inactivation time course of TEA-sensitive currents was voltage-dependent, becoming faster at more depolarized levels. The inactivation of TEA-sensitive currents almost recovered within 5 ms. 4-AP- and TEA-sensitive K(+) currents coexisted in the same IHC.