Aminoglycoside antibiotics inhibit maxi-K+ channel in single isolated cochlear efferent nerve terminals.
Patch clamp recordings were obtained from isolated cochlear efferent nerve terminals. The effect of aminoglycoside antibiotics on single maxi-K+ channels was determined. At positive voltages (cytosol with respect to extracellular side), neomycin, streptomycin, and kanamycin significantly reduced the single channel current amplitude of the maxi-K+ channel from the cytosolic side. The IC50 for neomycin was 9.10(-4) M from the cytosolic side and >> 10(-3) M from the extracellular side. Streptomycin and kanamycin were less potent. No significant difference in inhibition of the single channel current amplitude by 2.5.10(-4) M cytosolic neomycin was observed between 7.10(-4) M and 10(-6) M free cytosolic Ca2+. Neomycin had no significant effect on the open probability of the maxi-K+ channel either from the cytosolic or from the extracellular side. These findings demonstrate that the maxi-K+ channel in cochlear efferent nerve terminals can be a site of action for aminoglycoside antibiotics.
Takeuchi
S
S
Biophysics Laboratory, Boystown National Research Hospital, Omaha, Nebraska 68131.
Wangemann
P
P
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003056:Cochlear Nerve / Q000187:drug effects*; D004594:Electrophysiology; D005849:Gerbillinae; D066298:In Vitro Techniques; D007612:Kanamycin / Q000494:pharmacology; D009355:Neomycin / Q000494:pharmacology; D009476:Neurons, Efferent / Q000187:drug effects*; D015221:Potassium Channels / Q000187:drug effects*; D013307:Streptomycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D015221:Potassium Channels; D007612:Kanamycin; D009355:Neomycin; D013307:Streptomycin