Longitudinal comparisons of IHC ac and dc receptor potentials recorded from the guinea pig cochlea.

Recordings were made from inner hair cells (IHC) at three locations distributed in the apical half of the guinea pig cochlea. Longitudinal variations in ac and dc components of receptor potentials produced in response to single-tone inputs were studied to further understand the ways in which IHCs communicate with their innervating afferent dendrites. While neural synchrony probably depends on the ac receptor potential, discharge rate may be controlled by the dc receptor potential generated by the IHC transducer plus an ac component derived from the phasic receptor potential. The latter reflects low-pass filtering inherent in the hair cell's basolateral membrane and calcium-dependent synaptic processes. By comparing the frequency dependence of ac and dc components in cells with different characteristic frequencies, it may be possible to learn how neural response areas are formed and why their shapes change along the cochlear spiral.