碩士 / 國立成功大學 / 生理學研究所 / 96 / Tinnitus is the most prevalent hearing disorder and patients affected seriously may even commit suicide. Its patho-physiological mechanisms remain obscure and there is no effective cure for tinnitus to this day. Over-doses of salicylate (SA) are well-known to induce tinnitus in humans and behavioral evidence suggested similar effects in animals. Here we aimed to understand the underlying mechanisms of tinnitus by studying changes in auditory evoked potential (AEP) in animals receiving tinnitus-inducing doses of SA. Adult rats, after chronic implantation of epidural low impedance electrodes at the auditory cortex and full recovery from surgery, AEPs were recorded in the conscious state and results were analyzed for possible changes within 3 hours after SA injections (250 mg/kg/day, i.p.) for 5 consecutive days. A variety of sounds were used to evoke auditory potentials, including single click, click trains and tone bursts of various frequencies. Response changes were rather consistent across the 5 days and across animals. Average AEP integrals in the post- stimulus 28 ms were taken as response measure to tone bursts or clicks after SA treatment and in addition signs of loudness recruitment. SA invariably increased the response amplitude of averaged AEP to all sounds tested (p<0.001) and simultaneously reduced their response thresholds. Results were interpreted to reflect mainly cortical components of the hyperacusis associated with the SA-induced tinnitus. The changes in AEP to narrow band signals like tones are more easily interpreted than to broad band signals like clicks. Our finding of elevated gains in the AEP response-level function is consistent with a higher frequency-band activation of the auditory descending pathways, arising likely after SA-suppression of hearing sensitivity at the lower brainstem.
| Identifer | oai:union.ndltd.org:TW/096NCKU5116005 |
| Date | January 2008 |
| Creators | I-lynn Wan, 萬怡伶 |
| Contributors | Wai-Fung Poon, 潘偉豐 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 88 |
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