The role of ear stone size in hair cell acoustic sensory transduction

Maya Inoue,Masashi Tanimoto,Yoichi Oda

doi:10.1038/srep02114

Maya Inoue, Masashi Tanimoto + Show 1 more

Open Access

https://doi.org/10.1038/srep02114

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Abstract

Hearing and bodily balance are different sensations initiated by a common mechanism. Both sound- and head movement-dependent mechanical displacement are converted into electrical signals by the sensory hair cells. The saccule and utricle inner ear organs, in combination with their central projections to the hindbrain, are considered essential in fish for separating auditory and vestibular stimuli. Here, we established an in vivo method in larval zebrafish to manipulate otolith growth. We found that the saccule containing a large otolith is necessary to detect sound, whereas the utricle containing a small otolith is not sufficient. Otolith removal and relocation altered otolith growth such that utricles with experimentally enlarged otoliths acquired the sense of sound. These results show that otolith biomineralization occurs in a region-specific manner, and suggest that regulation of otolith size in the larval zebrafish ear is crucial to differentially sense auditory and vestibular information.

Highlights

Hearing and bodily balance are different sensations initiated by a common mechanism
We observed that a sound stimulus (90–108 dB sound pressure level [SPL] at 500 Hz; Fig. 1h lower waveform) elicited negative-going microphonic potentials (MPs) in the otic vesicle (OV), with peaks that occurred at twice the sound frequency (Fig. 1e)[14,15]
To determine whether the U or S responded to sound stimulus in larvae, we removed the otolith from each macula in either the www.nature.com/scientificreports they were coupled with an enlarged otolith

Summary

Introduction

Hearing and bodily balance are different sensations initiated by a common mechanism. Both sound- and head movement-dependent mechanical displacement are converted into electrical signals by the sensory hair cells. The otolith acts as an inertial mass, and sound- and head movement-evoked acceleration produces relative displacement between the otolith and the coupled hair cells due to the difference in their inertia This displacement mechanically deflects the hair bundles and opens mechanotransduction channels, which subsequently can produce a receptor potential[3,4]. Behavioural studies that eliminate the otolith organ in fish reveal the functional differences between the three otolith organs: the saccule (S) and lagena (L) are necessary for auditory perception and the utricle (U) is essential for postural equilibrium[2,8,9] The mechanisms underlying their functional differentiation, remain unclear. Focusing on the size difference between the S and U otoliths, we examined whether otolith manipulation could affect sound-evoked microphonic potentials (MPs), which reflect hair cell mechanotransduction responses

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