Property of IK,n in inner hair cells isolated from guinea-pig cochlea

One of the potassium currents, IK,n, is already activated at the resting potential of the cell and thus determines the membrane potential. KCNQ4 channel has been identified as the molecular correlate of IK,n. In the present study, we measured IK,n in acutely isolated IHCs of guinea-pig cochlea using the whole-cell voltage-clamp techniques, and investigated the properties of the currents. IK,n was 70% activated around the resting potential of −60mV and deactivated on hyperpolarization. IK,n was blocked by the KCNQ-channel blockers, linopirdine (100μM) and XE991 (10μM), but was insensitive to both IK,f blocker, tetraethylammonium (TEA), and IK,s blocker, 4-aminopyridine (4-AP). There was no significant difference in the size of IK,n between the apical and basal turn IHCs.