ABSTRACT
OBJECTIVE To investigate the effects of simulated noise-weightlessness combined factors on auditory brainstem response thresholds and the cochlear structure after a medium-long term (2-8 weeks). METHODS Healthy adult rats were randomly divided into male/female experimental and control groups. The male and female experimental groups were exposed to simulated noise-weightlessness environment and exerted impulse noise exposure at the end. Auditory brainstem response (ABR) threshold was recorded at the beginning, the 2nd, 4th and 8th weeks and after impulse noise exposure exerting. The cochlea was also examined by scanning electron microscopy each time after ABR threshold record. RESULTS ABR thresholds in experimental groups after impulse noise exposure were significantly increased (P<0.05). Female experimental group were lower than those of the male experimental group at 2 and 4 weeks (P<0.05). Scanning electron microscope observation showed that the inner and outer hair cell were losing and lodging, and the longer exposed to the compound factors, the heavier pathological changes observed on the cochlear hair cell. CONCLUSION Noise-weightlessness combined factors can cause the morphology and function damage of rat cochlear in medium-long term. The damage of impulse noise was more than steady noise on rat auditory function. Sex differences was also observed. Rat cochlear hair cell pathological changes increased with the exposed time.