Effect of inner ear ischemia/reperfusion on cochlea

Objective To study the effect of inner ear ischemia/reperfusion on cochlea. Methods Guinea pigs were randomly allocated into normal group, 30min ischemia group, 30min ischemia/reperfusion group, 60min ischemia group, and 60min ischemia/ reperfusion group. Anterior inferior cerebellar artery（AICA） was exposed at surgery via the base of skull. In ischemia group, a small piece of filter paper containing 5ul FeCl₃ was placed upon the AICA to induce formation of thrombus. In reperfusion group, animals were injected with urokinase （UK） through the left external jugular vein after the formation of thrombus. Blood flow in cochlea was monitored continuously with a laser Doppler flow meter. ABR and DPOAE were tested before and after each experiment. Then, surface preparation samples of basilar membrane were stained with AgNO₃ and observed under a light microscope. Results After administration of FeCl₃, the blood flow in cochlea was declined to 30% of the base level. In reperfusion group, the blood flow in cochlea was returned to 70% of the base level after injection of UK. The longer the ischemia was, the higher the ABR threshold was. The damage was severer to outer hair cells than to inner hair cells. Conclusion Ischemia/reperfusion can induce injury of cochlea.