Single Channel Recordings of Calcium Currents in Chick Cochlear Hair Cells

Single Ca2+ channel currents were recorded from chick cochlear hair cells by using cell-attached patches. The elementary current was about - 2 pA at 70 mV positive to the resting potential (R.P.+ 70 mV); the slope conductance over a 40 mV voltage range was 24 pS. The open time histogram was reasonably well expressed by a single exponential function, while the closed time histogram was expressed by a sum of two exponential functions. The Ca2+ channel was activated around R.P.+ 60 mV and the average ensemble current did not decay during 130 ms depolarization, suggesting that the Ca2+ channel in chick cochlear hair cells is the L-type. The Ca2+ channel has three modes of gating behavior, expressed as current records with brief openings (mode 1), no openings (mode 0), or long-lasting openings and very brief closings (mode 2).