Acute treatment of noise trauma with local caroverine application in the guinea pig

Intense sound stimulation may result in excessive glutamate release from the inner hair cells, resulting in binding to the post-synaptic glutamate receptors and leading to neuronal degeneration and functional impairment. In this study we investigated the therapeutic effect and time window of caroverine, an N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist, on noise-induced hearing loss. Guinea pigs were exposed to one-third octave band noise centered at 6.3 kHz (110 dB sound pressure limit) for 1 h. One or 24 h after noise exposure, caroverine was applied to the round window membrane. Auditory brainstem responses were recorded at regular time intervals. It was shown that caroverine could significantly decrease hearing impairment after noise trauma when applied 1 but not 24 h after noise exposure.