Keywords: 
• noise induced hearing loss /
• auditory brainstem response /
• α-lipoic acid /
• protective effect /
• preventive effect

Abstract: Objective To observe the protection of free radical scavenger: α-lipoic acid on the explosive hearing loss in rats. Methods 24 pure white male guinea pigs weighted between 250~300 g, which were randomly divided into α-lipoic acid low, medium, high group(n=3×6), Noise controlled group(n=6). Each group of animals was exposed to octave band noise (4 kHz center frequency) 115 dB SPL 4 h. α-Lipoic acid group were administered α-lipoic acid 30 mg/(kg·d), 60 mg/(kg·d), 120 mg/(kg·d) for 10 days (2 days before the exposure, 7 days after); Noise controlled group animals were given normal saline orally. After exposure, auditory brainstem response (ABRs) was tested in animals in each group at different times; hair cell loss and damage were examined through histological means. Results After exposure of 3 days, lower/middle/ high dose group had significant differences with noise control group at frequencies 8, 16 kHz; low and high dose group had significant differences with noise control group at frequencies 24, 32 kHz; 7 days after exposure, middle/ high dose group had significant differences with noise control group at frequencies of 8, 16, 24 kHz), low and high dose group had significant differences with noise control group at frequencies 32 kHz; after 10 days, high dose group had significant differences with noise control group at each frequencies. In the histological examination, animals of three α-lipoic acid dose group were found little inside and outside hair cell loss or damage. Noise controlled animals showed outer hair cells in the ear edema/vacuolar degeneration and other diseases. Conclusions Low, middle, high doses of a-lipoic acid on the explosive hearing loss had a preventive effect. High dose α-lipoic acid could take a good prevention and treatment in noise-induced hearing loss.