Kinetic analysis of barium currents in chick cochlear hair cells

M. Zidanic, Paul Albert Fuchs

Research output: Contribution to journalArticle

Abstract

Inward barium current (I(Ba)) through voltage-gated calcium channels was recorded from chick cochlear hair cells using the whole-cell clamp technique. I(Ba) was sensitive to dihydropyridines and insensitive to the peptide toxins ω-agatoxin IVa, ω-conotoxin GVIa, and ω-conotoxin MVIIC. Changing the holding potential over a -40 to -80 mV range had no effect on the time course or magnitude of I(Ba) nor did it reveal any inactivating inward currents. The activation of I(Ba) was modeled with Hodgkin-Huxley m2 kinetics. The time constant of activation, τ(m), was 550 μs at -30 mV and gradually decreased to 100 μs at +50 mV. A Boltzmann fit to the activation curve, m(x), yielded a half activation voltage of -15 mV and a steepness factor of 7.8 mV. Opening and closing rate constants, α(m) and β(m), were calculated from τ(m) and m(∞), then fit with modified exponential functions. The H-H model derived by evaluating the exponential functions for α(m) and β(m) not only provided an excellent fit to the time course of I(Ba) activation, but was predictive of the time course and magnitude of the I(Ba) tail current. No differences in kinetics or voltage dependence of activation of I(Ba) were found between tall and short hair cells. We conclude that both tall and short hair cells of the chick cochlea predominantly, if not exclusively, express noninactivating L- type calcium channels. These channels are therefore responsible for processes requiring voltage-dependent calcium entry through the basolateral cell membrane, such as transmitter release and activation of Ca2+-dependent K+ channels.

Original languageEnglish (US)
Pages (from-to)1323-1336
Number of pages14
JournalBiophysical Journal
Volume68
Issue number4
StatePublished - 1995
Externally publishedYes

Fingerprint

Auditory Hair Cells
Barium
Conotoxins
Agatoxins
Dihydropyridines
L-Type Calcium Channels
Cochlea
Calcium Channels
Cell Membrane
Calcium
Peptides

ASJC Scopus subject areas

  • Biophysics

Cite this

Kinetic analysis of barium currents in chick cochlear hair cells. / Zidanic, M.; Fuchs, Paul Albert.

In: Biophysical Journal, Vol. 68, No. 4, 1995, p. 1323-1336.

Research output: Contribution to journalArticle

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