Protection against noise-induced cochlear hair cell loss in conditioned guinea pigs

Since noise-induced hearing loss is a common problem and its prevention is important, we aimed to evaluate whether previous exposure to moderate level of noise could prevent subsequent high level noise-induced cochlear damage. This study was conducted on 10 guinea pigs randomly divided into two groups (n=5, each). Animals in control group exposed to 4 kHz, 105 dB SPL octave band noise for 4 hours, while in conditioned group animals exposed to 85 dB SPL, 4 kHz octave band noise, 6 hours/day for 5 days before exposing to 105 dB noise. One week later, the subjects euthanized for histological evaluationand the remaining and lost outer hair, inner hair and supporting cells were compared. Our results showed that outer hair cells row 1 was injured the most. A massive damage around the second turn of the cochlea was observed in control group. Conditioning significantly reduced the amount of hair cell loss. In conditioned group, the amount of hair cell loss was significantly reduced when compared to control (p < 0/05). Our findings confirmed that conditioning protects against noise-induced cochlear hair cell loss.