The Synergistic Effects of Simulated Microgravity and Noise Exposure on Damage of Auditory Function and Corti Organs in Rat / 听力学及言语疾病杂志

ABSTRACT

Objective To investigate the synergistic effects of simulated microgravity and noise on the audito‐ry functions and corti organs in rats .Methods A total of 48 healthy rats were randomly divided into 4 groups (n=12)control group (Group A) ,microgravity only group (Group B) ,noise only group (Group C) and microgravity+noise group (Group D) .The microgravity environment was simulated by suspending the posterior limb using Morey-Holton method .The noise exposure was the simulation of the noise environment in spaceship including steady -state noise (72 ± 2) dB SPL and impulse noise up to 160 dB SPL .The control group was kept in normal conditions without any exposure .Auditory brainstem responses (ABRs) ,HE stainings ,immunofluorescence stainings and scanning electron microscopes (SEMs) were tested after 1week and 2 weeks exposure respectively (n=6) .Results The average of ABR threshold shifts of 2 weeks exposure were higher than those of 1 week in each group .Group D showed the highest ABRs (P<0 .01) .The HE stainings showed different degrees of injury in corti organs in all experimental groups ;which Group D being the most serious ,followed by Group C .The results of immunefluorescence in hair cells showed that swelling necrosis was the main damage of cochlear hair cell after 1 week's exposure .The swelling rate of Group D was the highest ,followed by Group C .Nucleus missing in hair cells was observed after 2 weeks'exposure . Group D had the highest missing rate and the main missing of Group B happened in the inner hair cells .SEM showed that the most serious damage of stereociliums in Group D ,followed by Group C ,then Group B .Conclusion The synergistic effects of simulated microgravity and noise lead to significant damage of the auditory function and cochlea Corti organs in rat .