Effects of N-Acetylcysteine on Auditory Brainstem Response Threshold Shift in Rabbits Exposed to Noise and Carbon Monoxide

Problem statement: Noise Induced Hearing Loss (NIHL) is one of the most important occupational disease in worldwide. NIHL has been found to be potentiated by simultaneous Carbon monoxide (CO) exposure. Exposure to noise plus CO is common in occupational and environmental settings. Free radicals have been implicated in cochlear damage resulting from exposure to noise and due to CO hypoxia This study examined whether N-Acetylcysteine (NAC) administration cause attenuation of Auditory Brainstem Response (ABR) threshold shifts resulting from noise exposure and noise plus CO exposure. Approach: Forty-two rabbits were divided into seven groups including control, noise+ saline, noise+ CO +saline, noise+ NAC, noise+ CO+ NAC, CO+ NAC and NAC alone. ABR was assessed before exposure, 1 hour and 14 days post exposure. Results: The administration of 325 mg kg^-1 of NAC prior, following and post exposure to noise or noise plus CO recovered permanent ABR threshold shift at 1 and 2 kHz almost to the baseline and provided significant attenuation in permanent ABR threshold shift at 4 and 8 kHz in subjects which were exposed to noise but it did not block the potentiating of threshold elevation by CO exposure (extra threshold loss by combined exposure) at 4 and 8 kHz. Conclusion: NAC provides protective effect against hearing loss resulting from noise exposure and simultaneous exposure to noise plus CO.