Transient increase in cytosolic free calcium evoked by repolarization in type I vestibular hair cells of rats.
Simultaneous whole-cell patch clamp and Fura-2 microfluorimetric recordings of membrane currents and intracellular free calcium concentration ([Ca2+]i) were made from type I vestibular hair cells isolated from cristae ampullares of adult rats. Cells held between -110 or -70 mV and depolarized up to -20 mV did not evoke any [Ca2+]i changes for any duration of the membrane depolarization (up to 3 s). Returning the membrane to repolarizing potential induced a transient [Ca2+]i increase. At the pulse break, an inward current was evoked. The [Ca2+]i increase and inward current amplitude were dependent on the duration and the amplitude of the previous depolarization. A liminar value of membrane depolarization of -55 +/- 3 mV (mean resting potential -62 +/- 7 mv) had to be applied to induce [Ca2+]i increase upon subsequent repolarization. [Ca2+]i response and inward current could not be evoked in calcium-free solution. Both responses were restored when calcium was added to the medium.
Griguer
C
C
INSERM, U.432, Université Montpellier II, France.
Chabbert
C
C
Sans
A
A
Lehouelleur
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D016257:Fura-2; D018069:Hair Cells, Vestibular / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D018408:Patch-Clamp Techniques; D051381:Rats
D002118:Calcium; D016257:Fura-2