Effects of Noise and Salicylate on Hair Cell Loss in the Chinchilla Cochlea

Chinchillas were exposed to octave band noise, sodium salicylate (300 mg/kg per day intraperitoneally), or the combination of both agents for 15 days. The octave band noise exposure was centered at 500 Hz at an intensity of either 80 or 105 dB sound pressure level. The effects of the experimental treatments were evaluated by determining the number of missing hair cells after recovery as a function of location within the cochlea using a surface preparation technique. Average cochleograms were calculated for each of five experimental groups. Animals given salicylate alone showed little or no hair cell loss. Noise exposure at 80 dB resulted in a mild (less than 30%) outer hair cell loss in the apical turn of the cochlea, whereas exposure at 105 dB resulted in moderate (50%) outer hair cell loss (outer hair cell first row particularly) in the apical half of the cochlea, mild outer hair cell loss in the basal region of the cochlea, and a mild loss of inner hair cells. The amount of hair cell loss in the groups exposed to the combination of salicylates and noise was not significantly different from the corresponding groups exposed to noise alone. Statistical analysis of the data suggest that the combination of salicylate plus noise does not produce any greater hair cell loss than noise alone.