Expression And Significance Of GAP-43 And ARC In Auditory Cortex Of Rats Experienced Tinnitus

Background and purposesTinnitus is a symptom of otology, without any outside sound source or electrical stimulation of the ear or head while the sound produced by feel. The formation mechanism of tinnitus has not yet entirely clear, a number of studies have shown that the occurrence of tinnitus and maintenance is related to auditory cortex plasticity. ARC gene (activity regulated cytoskeleton associated protein,Arc/Arg3.1) and GAP-43 gene (growth associated protein,GAP-43) reflect the activities of neuronal function and play an important role in the formation of synaptic connections and early changes in neuronal plasticity.They are the molecular markers of the nervous plasticity and regeneration.In this study, we used fluorescence quantitative PCR technique to detect the changes of the expression of GAP-43 and ARC in auditory cortex of the tinnitus rats to explore the neuronal plasticity changes in auditory cortex of rats experienced tinnitus.Materials and methods1. Developing the animal model of tinnitus.2. The auditory threshold and latency were tested with ABR(auditory brainstem response,ABR) instrument before behanvior training and sacrifice respectively.3. Fluorescence quantitative PCR was used to investigate the expression of GAP-43 and ARC in the auditory cortex.Results 1. The success of developing animal model of tinnitus indicated the rats after injection of sodium salicylate did feel tinnitus.2. In normal rats, ABR waveforms were stability. But rats after repeated injections of sodium salicylate , ABR waveforms were poorly differentiated, the amplitude decreased, ABR thresholds increased, II-wave latency was prolonged, as compared with the pre-test, there are statistics significance.3. GAP-43 and ARC protein expression of auditory cortex in the sodium salicylate groups was significantly higher than the other three control groups. The difference was statistically significant.Conclusions1.The behavioral experiment confirms that the rates experienced tinnitus after salicylate injection.2.The ABR threshold shfit and prolongation of wave II latency induced by sodium solicylate injection indicated that salicylate may cause changes of neuroeletricity in the inner ear ,it can provide objective evidence of the audiology.3.The higher expression of GAP-43 and ARC suggests that there are neuronal plasticity occurring in the auditory cortex.