Protective effect of N-acetylcysteine on blocking potentiation of noise induced hearing loss by Carbon monoxide in rabbits

Noise induced hearing loss (NIHL) is one of the most important occupational diseases worldwide. NIHL has been found to be potentiated by simultaneous carbon monoxide (CO) exposure. This study was performed to evaluate the protective effect of N- acetylcysteine (NAC) administration on potentiating effect of CO on NIHL in rabbits. In this experimental study forty-two male adult white rabbits were divided into seven groups (n=6 for each group). Group 1, as control (no exposure to noise or CO and no injection); Group 2, noise exposure (100 dB for 40 h); Group 3, noise+CO exposure; Group 4, noise exposure+NAC administration (325 mg/kg); Group 5, noise+CO exposure+NAC administration, Group 6, NAC administration alone and Group 7, CO exposure (700 ppm for 40h). Audiometric test of rabbits was assessed by Auditory Brain stem Response (ABR) test in three stages: before exposure, 1 hour and 14 days post exposure at 1, 2, 4 and 8 kHz frequency. The administration of NAC attenuated temporary and permanent ABR threshold shift caused by noise exposure and simultaneous exposure to noise plus CO. NAC administration blocked the potentiating of temporary threshold shift by CO at 1, 2, and 4 KHz frequency and also blocked potentiating of permanent threshold shift by CO at all frequencies. NAC as an antioxidant agent can attenuate temporary and permanent noise induced ABR threshold shifts and provides protective effect against potentiating of NIHL by CO in rabbits.