THE GENERATION OF DC POTENTIALS IN A COMPUTATIONAL MODEL OF THE ORGANOF CORTI - EFFECTS OF VOLTAGE-DEPENDENT K+ CHANNELS IN THE BASOLATERAL MEMBRANE OF THE INNER HAIR CELL

A computational model of the organ of Corti is described to assist in the interpretation of electrophysiological data concerning the role of the K+ channels residing in the basolateral membrane of cochlear hair tells. Recent in vivo data from Van Ernst et al. (Hear. Res. 88, 27-3 5 (1995); Hear. Res. 102, 70-80 (1996)) about the effects of selective blocking of Ki channels indicate that these channels affect the magni tude of the summating potential. In order to understand the nature of this effect, the model of Dallos (Hear. Res. 14, 281-291 (1984)) was e xtended to account for the voltage- and time-dependent properties of t he K+ channels in the basolateral membrane of the inner hair cell (IHC ) (Kros and Crawford, J. Physiol. 421, 262-291 (1990)). The model show s that the K+ channels induce a shift in the mean IHC basolateral cond uctance when high-frequency stimuli are present. As a result, cochlear transduction shifts to a different electrical operating state and thi s is the source of a marked decrease in the stimulus-evoked DC respons e of the IHC. Extracellularly. in contrast, the magnitude of the DC re sponse increases slightly. At low frequencies, the K+ channels respond to the stimulus waveform on a Cycle-by-cycle basis. The waveform dist ortion associated with this dynamic basolateral impedance induces a fu rther decrease in the intracellular stimulus-evoked DC response of the IHC. Thus, K+ channels in the IHC appear to be directly involved in t he generation of the DC receptor potential at low frequencies, but at high frequencies they simply modify the size of the DC response. (C) 1 998 Elsevier Science B.V.