Hearing Assessment in Zebrafish During the First Week Postfertilization.

The zebrafish (Danio rerio) is a valuable vertebrate model for human hearing disorders because of many advantages in genetics, embryology, and in vivo visualization. In this study, we investigated auditory function of zebrafish during the first week postfertilization using microphonic potential recording. Extracellular microphonic potentials were recorded from hair cells in the inner ear of wild-type AB and transgenic Et(krt4:GFP)(sqet4) zebrafish at 3, 5, and 7 days postfertilization in response to 20, 50, 100, 200, 300, and 400-Hz acoustic stimulation. We found that microphonic threshold significantly decreased with age in zebrafish. However, there was no significant difference of microphonic responses between wild-type and transgenic zebrafish, indicating that the transgenic zebrafish have normal hearing like wild-type zebrafish. In addition, we observed that microphonic threshold did not change with the recording electrode location. Furthermore, microphonic threshold increased significantly at all tested stimulus frequencies after displacement of the saccular otolith but only increased at low frequencies after displacement of the utricular otolith, showing that the saccule rather than the utricle plays the major role in larval zebrafish hearing. These results enhance our knowledge of early development of auditory function in zebrafish and the factors affecting hearing assessment with microphonic potential recording.