Noise-Induced Hypersensitization of the Acoustic Startle Response in Larval Zebrafish

Overexposure to loud noise is known to lead to deficits in auditory sensitivity and perception. We studied the effects of noise exposure on sensorimotor behaviors of larval (5-7 days post-fertilization) zebrafish (Danio rerio), particularly the auditory-evoked startle response and hearing sensitivity to acoustic startle stimuli. We observed a temporary 10-15 dB decrease in startle response threshold after 18 h of flat-spectrum noise exposure at 20 dB re·1 ms^-2. Larval zebrafish also exhibited decreased habituation to startle-inducing stimuli following noise exposure. The noise-induced sensitization was not due to changes in absolute hearing thresholds, but was specific to the auditory-evoked escape responses. The observed noise-induced sensitization was disrupted by AMPA receptor blockade using DNQX, but not NMDA receptor blockade. Together, these experiments suggest a complex effect of noise exposure on the neural circuits mediating auditory-evoked behaviors in larval zebrafish.