Quantification of vestibular-induced eye movements in zebrafish larvae.
BACKGROUND
Vestibular reflexes coordinate movements or sensory input with changes in body or head position. Vestibular-evoked responses that involve the extraocular muscles include the vestibulo-ocular reflex (VOR), a compensatory eye movement to stabilize retinal images. Although an angular VOR attributable to semicircular canal stimulation was reported to be absent in free-swimming zebrafish larvae, recent studies reveal that vestibular-induced eye movements can be evoked in zebrafish larvae by both static tilts and dynamic rotations that tilt the head with respect to gravity.


RESULTS
We have determined herein the basis of sensitivity of the larval eye movements with respect to vestibular stimulus, developmental stage, and sensory receptors of the inner ear. For our experiments, video recordings of larvae rotated sinusoidally at 0.25 Hz were analyzed to quantitate eye movements under infrared illumination. We observed a robust response that appeared as early as 72 hours post fertilization (hpf), which increased in amplitude over time. Unlike rotation about an earth horizontal axis, rotation about an earth vertical axis at 0.25 Hz did not evoke eye movements. Moreover, vestibular-induced responses were absent in mutant cdh23 larvae and larvae lacking anterior otoliths.


CONCLUSIONS
Our results provide evidence for a functional vestibulo-oculomotor circuit in 72 hpf zebrafish larvae that relies upon sensory input from anterior/utricular otolith organs.
Mo
Weike
W
Howard Hughes Medical Institute, Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
Chen
Fangyi
F
Nechiporuk
Alex
A
Nicolson
Teresa
T
D000465:Algorithms; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000502:physiology; D003627:Data Interpretation, Statistical; D005123:Eye / Q000254:growth & development; D005133:Eye Movements / Q000502:physiology*; D005583:Fourier Analysis; D007091:Image Processing, Computer-Assisted; D007259:Infrared Rays; D007814:Larva; D009154:Mutation; D010037:Otolithic Membrane / Q000502:physiology; D010775:Photic Stimulation; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D012399:Rotation; D014722:Vestibule, Labyrinth / Q000502:physiology*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology
D015820:Cadherins; D029961:Zebrafish Proteins; C499092:cdh23 protein, zebrafish
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