SODIUM AND POTASSIUM CURRENTS OF TYPE-I SPIRAL GANGLION-CELLS FROM RAT

Ion channel activity of acutely dissociated type I spiral ganglion cel ls isolated from rats was investigated using the whole-cell variation of the patch clamp technique. Tetrodotoxin-sensitive sodium current an d tetraethylammonium-sensitive potassium current were recorded. With a holding potential of - 80 mV, peak sodium currents were generated by depolarizations to membrane potentials more positive than - 50 mV. Pot assium currents were elicited at membrane potentials more positive tha n - 40 mV. Some cells which did not exhibit sodium current exhibited d elayed rectifier potassium currents. Steady-state sodium channel inact ivation curve yielded a slope of 12 mV and a half-inactivated potentia l of - 83 mV. Recovery from inactivation of the sodium channel proceed ed with a fast and slow time course; recovery began as early as 0.8 ms and proceeded with a time constant of 7.5 ms. It is concluded that ty pe I spiral ganglion cells are endowed with sodium and potassium chann els which are responsible for generation and propagation of auditory n erve action potentials.