Abstract
We explore the effects of high-amplitude mechanical stimuli on hair bundles of the bullfrog sacculus. Under in vitro conditions, these bundles exhibit spontaneous limit cycle oscillations. Prolonged deflection exerted two effects. First, it induced an offset in the position of the bundle. Recovery to the original position displayed two distinct time scales, suggesting the existence of two adaptive mechanisms. Second, the stimulus suppressed spontaneous oscillations, indicating a change in the hair bundle’s dynamic state. After cessation of the stimulus, active bundle motility recovered with time. Both effects were dependent on the duration of the imposed stimulus. External calcium concentration also affected the recovery to the oscillatory state. Our results indicate that both offset in the bundle position and calcium concentration control the dynamic state of the bundle.
Highlights
Hair cells constitute the functional elements of the inner ear, as they transduce the mechanical vibrations into electrical signals that trigger action potentials in the auditory nerve [1,2]
We report on recordings from 57 saccular hair cell bundles (N~34 frogs) that exhibited spontaneous oscillations
Effect of Calcium As prior work has shown that calcium plays a modulatory role in active hair bundle motility [27,38,42], we explored its effects on the duration of the quiescent interval induced by prolonged deflection
Summary
Hair cells constitute the functional elements of the inner ear, as they transduce the mechanical vibrations into electrical signals that trigger action potentials in the auditory nerve [1,2]. These cells derive their name from a specialized organelle on their apical surface that consists of a bundle of actin-packed stereocilia organized in a quasi-crystalline array. Along one axis within the bundle’s array, pairs of neighboring stereocilia are connected by filamentous tip links [3,4], which are coupled to mechanically gated ion channels. The resulting influx of ions depolarizes the cell, leading to the release of neurotransmitter at the hair cell’s base
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