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.