Intracellular Calcium Suppresses Mechano-Electrical Transduction Current in Chick CochlearHair Cells

Abstract

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.

Defining features of the hair cell mechanoelectrical transducer channel

“…Indeed, elevating intracellular Ca 2+ blocks the hair cell MET channel [47] and causes adaptation [63]. Ca 2+ -induced activation in TRPP2 may underlie its intracellular role as a Ca 2+ release channel in endoplasmic reticulum [50], though its function is often dependent on interaction with adaptor proteins [8].…”