The fast activating potassium current, I-K,I-f, in guinea-pig inner hair cells is regulated by protein kinase A

The mammalian inner hair cell (IHC) responds to displacements produced in t he cochlea by sound by releasing neurotransmitter from its basal pole. A ba solateral fast activating potassium current, called I-K,I-f, allows IHCs to act as sensory cells at high frequencies by shortening the membrane time c onstant. This current is co-expressed with a slower activating current, I-K ,I-s We have studied the intracellular regulation of IHC currents using the whole-cell patch clamp technique in conjunction with agents that influence the function of protein kinase A (PKA). Bath applied 8-Bromo-cAMP, an acti vator of PKA, increased the amplitude of outwardly rectifying currents and shortened the exponential time constant of activation. Following blockade o f I-K,I-s by intracellular 4-AP, I-K,I-f could be reduced in amplitude by H -89, an inhibitor of PKA. Our results suggest that PKA regulates I-K,I-f an d so shapes the frequency response of IHCs. (C) 1999 Elsevier Science Irela nd Ltd. All rights reserved.