Dihydrostreptomycin Goes through the Mechano-Electric Transduction Channel in Chick Cochlear Hair Cells

Objective: This study evaluated the ability of dihydrostreptomycin (DHSM) to go through the mechano-electric transduction (MET) channels in hair cells under physiological conditions. Materials and Methods: Tall hair cells were isolated from the chick basilar membrane (cochlea). Mechanical stimulation was applied by a glass rod attached to a piezoelectric bimorph, and MET currents were recorded with a whole-cell patch technique. The voltage-dependent block of DHSM to MET channel was estimated by calculating the relative conductances (the ratio of MET current in DHSM saline to DHSM-free saline) at various membrane potentials. Results and Conclusion: At membrane potentials between –100 and +50 mV, DHSM behaves as a voltage-dependent blocker according to a partial block model. At membrane potentials more negative than –100 mV, however, DHSM blocking decreased. This finding differed from the partial block model, but indicated that DHSM escaped through the channel pore into the cytoplasm by acting as a permeant channel blocker due to the large electrical driving force.