The frequency dependence of receptor potentials in hair cells of the mouse utricle

Abstract

The mechanoelectrical transduction currents of hair cells in the mouse utricle adapt at varying rates to step deflections of the hair bundles. We consider contributions of this adaptation process and of input resistance and membrane capacitance to the frequency dependence of the receptor potential. Whole-cell recordings of transduction current and receptor potential were made from hair cells in the excised epithelium of the mouse utricle. Hair bundles were deflected by a fluid jet with step and sinusoidal waveforms. In type II cells, the receptor potential was a bandpass function of stimulus frequency. The adaptation rate of the transduction current, measured in response to step bundle deflections, accounted for much of the roll-off in the receptor potential at low frequencies of sinusoidal deflections. Corner frequencies predicted from the adaptation time course varied from 2 to 60 Hz. Voltage-gated conductances also contributed. Roll-off of the receptor potential at the high-frequency end may largely reflect input resistance and capacitance. Corner frequencies predicted by estimated membrane time constants varied from 30 to 150 Hz. In type I cells, slower or no adaptation and shorter membrane time constants predict larger response bandwidths. Frequency tuning in vivo will reflect other factors, including the mechanical response of the otolith and otolithic membrane to head movements.