Protective effects of midazolam on noised-induced hearing loss in guinea pigs / 西安交通大学学报(医学版)

ABSTRACT

Objective To investigate the protective effects of midazolam on noise-induced hearing loss in guinea pigs by testing reactive oxygen species (ROS) level in the cochlea and plasma SOD and MDA. Methods Totally forty male pigmented guinea pigs were randomly divided into four groups control (C) , midazolam (M), normal saline (S) and noise-induced deafened (D) groups, with ten guinea pigs in each. Groups M, S and D were exposed to a continuous noise (4kHz , octave band, 100dB SPL) 3h every day for 3 consecutive days. Group M was treated with midazolam, which was administered intramuscularly (0.1mg/kg) 24h before noise exposure, and immediately upon and during noise exposure. Group S was exposed to noise and treated with the same volume of normal saline intramuscularly, the time of injection was the same as that of Group M. Group C was not exposed to noise, but was treated with midazolam intramuscularly, the time of injection and the dosage were the same as those of Group M. Group S was exposed to noise and treated with normal saline intramuscularly ,the time of injection was same with that of Group M.Group D was exposed to noise only. All animals received auditory brainstem response (ABR) threshold recording before and immediately after noise exposure. Blood was collected when the guinea pigs were killed after the last ABR threshold recording, and serum SOD activity and MDA content were detected. Both the cochleae were removed and prepared for ROS assay. Results After noise exposure, ABR threshold shift (1.6±1.5) and ROS content [(291.10±2.30)u/mL] in Group M were significantly lower than those in Groups S and D [41.7±3.3, 44.3±3.9; (348.52±3.60)u/mL, (315.56±6.70)u/mL, P<0.05]. Serum SOD activity and MDA content were significantly increased in Group M, but the amplitude was less than that in Groups S and D.Conclusion Midazolam can prevent noise-induced hearing loss by reducing the increased ROS level in the cochlea after noise exposure.