The voltage-dependent Ca
2+ channel of the outer hair cells (OHCs) of cochlea plays an important role in the first step of sound perception. The effects of ototoxic drugs such as aminoglycoside antibiotics and platinum compounds on the voltage-dependent Ca
2+ channel of the OHCs of guinea pig cochlea were evaluated by microspectrofluorimetry and the whole-cell patch-clamp method. Neomycin and cisplatin (CDDP) blocked calcium entry into isolated OHCs evoked by [K+]-depolarization. CDDP blocked the voltage-dependent calcium current (
Ica) of isolated OHCs. These actions were observed in a concentration-dependent manner. Transplatin blocked
Ica to almost the same degree as CDDP, although it did not show any ototoxic or nephrotoxic effects. As previously reported by other investigators, Ca
2+ channel blockers such as nifedipine or inorganic antagonists for
Ica such as La
2+ which did not show ototoxicity also blocked the voltage-dependent Ca
2+ channel, suggesting that the antagonistic effect on the voltage-dependent Ca
2+ channel may alter cochlear function but does not directly cause cell death.
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