Effect of Ischemia-Induced Cochlear Inflammation on Auditory Responses in Male Rats

Ischemic injury is a major cause of hearing loss and oxidative stress is an important part of ischemic injury. The goal of this study was to evaluate the cochlear oxidative stress effect on auditory responses in male rats.

Cochlear oxidative stress was induced by bilateral carotid artery occlusion for 20 minutes. The rats were evaluated by biochemical inflammatory factors tumor necrosis factor-α [TNF-α] and C-reactive protein (CRP) in the day before and 1st, 4th, and 7th days following surgery. The auditory brainstem response (ABR) and electrocochleography (ECochG) were evaluated on the day before surgery and 14th, 21th and 28th days after surgery.

TNF-α and CRP levels concentrations increased one day after ischemia and subsequently decreased on the 7th day. The click and tone burst evoked ABR showed increased thresholds on day14th, 21th, and 28th. The highest threshold was recorded on day14th. The ECochG results also were abnormal for 55%, 70%, and 45% of cases on day 14th, 21th, and 28th, respectively.

Cochlear oxidative stress affects hearing sensitivity. The ABR shows elevated thresholds and abnormal ECochG was found in many cases.