头低位模拟失重状态对豚鼠耳蜗听功能与超微结构的影响

目的探讨头低位模拟失重对豚鼠耳蜗听功能与超微结构的影响。方法 22只豚鼠随机分为实验组16只和对照组6只。实验组采用头低位模拟失重法,身体纵轴与水平线呈-30°,于实验前、失重5天后即刻及脱离失重3天后分别测试豚鼠听性脑干反应(ABR),然后取耳蜗行扫描电镜和透射电镜观察。对照组不作任何处理。结果对照组豚鼠ABR反应阈为23.48±6.04dB SPL,实验组实验前为24.22±4.04,模拟失重5天后即刻ABR反应阈为41.61±7.01dB SPL,与实验前和对照组比较差异有显著统计学意义(P<0.05);脱离失重3天后实验组ABR反应阈为27.50±3.54dB SPL,与实验前相比差异无显著统计学意义(P>0.05)。扫描电镜观察发现失重5天后即刻豚鼠耳蜗内、外毛细胞散在缺失,纤毛融合、倒伏;透射电镜检查见内、外毛细胞细胞局部空泡形成,脱离失重3天后上述病变均有明显恢复,但未完全恢复正常。结论模拟失重5天即可以导致豚鼠耳蜗听觉功能和超微结构的损伤,脱离失重3天后听功能可以恢复正常,但其超微结构还没有完全恢复正常。

The Effects of Simulated Weightlessness on Auditory Function and Cochlea Ultrastructure in Guinea Pig

Objective To investigate simulated weightlessness induced effects on auditory function and ultrastructure of cochlea in a head-down guinea pig model. Methods A total of 22 guinea pigs were used in this experiment.All animals had normal eardrum and ear responsive before experiment.Guinea pigs were randomly divided into two groups.Sixteen guinea pigs were used for simulating weightlessness and six were served as control.Weightlessness was simulated by 30° head-down tilt for 5 days.Auditory brainstem response(ABR) was tested and the cochlea was examined by electron microscopy and transmission electron microscopy scanning before experiment,at day 5(at end of simulated weightlessness) and 3 days after recovery. Results Before the experiment,ABR threshold in control group(23.48±6.04 dB SPL) was not significanly different from that of in experimental group(24.22±4.04 dB SPL).After 5 days simulated weightlessness,ABR threshold in experimental group was 41.61±7.01 dB SPL which was significantly higher than the initial value(P<0.05).After 3 days reconvery,ABR threshold decreased to 27.5±3.54 dB SPL which was no significanly different from that of before the experiment(P>0.05).Simulated weightlessness for five days the outer hair cells were scattered Absent,and cilia were integrated and lodged in cochlea observed with electron microscope.Under transmission electron microscope,the inner and outer hair cells in cochlea were vacuolized.These changes in cochlea were significantly restored after three days recovery. Conclusion Simulated weightlessness can lead to temporary damage of auditory function in guinea pigs.and the damage can be restored after 3 days of recovery,However,ultrastructure changes in cochlea induced by simulated weightlessness can not be fully recovered 3 days later.