Electrical filtering in gerbil isolated type I semicircular canal hair cells.
1. Membrane potential responses of dissociated gerbil type I semicircular canal hair cells to current injections in whole cell current-clamp have been measured. The input resistance of type I cells was 21.4 +/- 14.3 (SD) M omega, (n = 25). Around the zero-current potential (Vz = -66.6 +/- 9.3 mV, n = 25), pulsed current injections (from approximately -200 to 750 pA) produced only small-amplitude, pulse-like changes in membrane potential. 2. Injecting constant current to hyperpolarize the membrane to around -100 mV resulted in a approximately 10-fold increase in membrane resistance. Current pulses superimposed on this constant hyperpolarization produced larger and more complex membrane potential changes. Depolarizing currents > or = 200 pA caused a rapid transient peak voltage before a plateau. 3. Membrane voltage was able to faithfully follow sine-wave current injections around Vz over the range 1-1,000 Hz with < 25% attenuation at 1 kHz. A previously described K conductance, IKI, which is active at Vz, produces the low input resistance and frequency response. This was confirmed by pharmacologically blocking IKI. This conductance, present in type I cells but not type II hair cells, would appear to confer on type I cells a lower gain, but a much broader bandwidth at Vz, than seen in type II cells.
Rennie
K J
KJ
Department of Otolaryngology, University of Texas Medical Branch, Galveston 77555-1063, USA.
Ricci
A J
AJ
Correia
M J
MJ
D000818:Animals; D004594:Electrophysiology; D005849:Gerbillinae; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D012665:Semicircular Canals / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D013757:Tetraethylammonium Compounds