Potassium currents in type II vestibular hair cells isolated from the guinea-pig's crista ampullaris

Publisher Website
Google Scholar
Abstract
Type II vestibular hair cells were isolated from cristae ampullares of guinea-pig and maintained in vitro for 2–3 h. Outward membrane currents were studied under whole-cell voltage-clamp conditions. Type II hair cells had resting potentials of about −45 mV. Depolarizing voltage steps from a holding potential of −80 or −90 mV induced time- and voltage-dependent outward currents which slowly decayed to a sustained level. Tail currents reversed at about −70 mV, indicating that the outward currents were mainly carried by potassium ions. The currents had an activation threshold around −50 mV. The transient component was completely removed by a depolarizing pre-pulse positive to −10 mV. While bath application of 4-aminopyridine (5 mM) reduced both components, extracellular tetraethylammonium (10 mM) or zero calcium preferentially diminished the sustained current. We conclude that at least two potassium conductances are present, a delayed rectifier with a relatively fast inactivation and a calcium-dependent potassium current. Depolarizing current injections induced an electrical resonance in the voltage responses, with a frequency of 25–100 Hz, larger currents causing higher frequencies.