The Mechanism of Hearing Loss after Focal Cerebral Ischemia-reperfusion Injury / 听力学及言语疾病杂志

ABSTRACT

Objective To investigate the mechanism of hearing loss after focal cerebral ischemia-reperfusion injury in rats.Methods A total of 60 healthy male adult SD rats were included in this study and randomly divided into 2 groups, ischemia-reperfusion(I/R) group and sham operated control, with 30 rats in each group.The rats in I/R group were operated for suture-occluded method to establish middle cerebral artery occlusion(MCAO)model, with ischemia for 60 mins followed by reperfusion for 24 hrs.The control group was only to be isolated cervical vessels, with no thread embolism inserted.The auditory brainstem response (ABR) was tested before operation and at 24 hrs post-operation respectively.At 24 hrs post-operation, we scored neurological functions, measured the changes of water content in the brain using the dry-wet weight method, and determined the infarct volume through TTC method.We also evaluated the integrity of blood-brain barrier(BBB) by viewing the exudation of Evans blue and observed the apoptosis of neurocyte by TUNEL method to conclude apoptotic index(AI).The expression of MMP-9,Claudin-5,Occludin and CX-43 were detected by Western blot.Results Compared with the sham group,the neurological function scores,the infarct volume and water content of the brain increased, with the elevated thresholds of ABR significantly and AI went up in I/R group.The expression levels of MMP-9 and CX-43 were significantly up-regulated,but the expressions of Claudin-5 and Occludin were obviously down-regulated.All of the differences above had statistical significances.Conclusion The mechanism of hearing loss after focal cerebral ischemia-reperfusion injury in rats is possibly related to MMPs activation,neurocyte apoptosis,BBB breakage and gap junction damage.