Intracellular calcium suppresses mechano-electrical transduction current in chick cochlear hair cells

Intracellular calcium concentration ([Ca2+](i)) was elevated by photolysis of the caged calcium compound, Nitr-5, and by use of the intrapipette perfusion technique in hair cells dissociated from the chick cochlea. An increase in [Ca2+](i) induced an outward-going current at a membrane potential of-40 mV, as recorded with an intracellular medium of 160 mM KCl. This current was carried by the Ca2+-activated K+ current. In contrast, an increase of [Ca2+](i) induced an inward-going current at -50 mV with a 160 mM CsCl-based intracellular medium. This inward-going current was carried by the Ca2+-activated non-selective cation current. The amplitude of the mechano-electrical transduction current was suppressed by the increase of [Ca2+](i), achieved both by photolysis and by use of the intrapipette perfusion method.