Changes In Parvalbumin Immunoreactivity In Rat Auditory Cortex Following Noise Exposure

Objective Observing the changes of auditory brainstem response(ABR) and the expression of Parvalbumin(PV) in auditory cortex after noise expose, research the influence of Parvalbumin expression level after rats’ noise exposure. And finally, discuss the possible mechanisms of auditory diseases like noise induced hearing loss,tinnitus and other auditory abnormality.Methods 31 normal male SD rats were divided into two groups, controls group(15 rats) and test group(16 rats). Test group were unilaterally exposed to 1 octave-band noise that the peak intensity is 116 d B sound-pressure level(SPL) centered at 16 k Hz for 1 h, to determine if noise expose caused changes of ABR and PV in the auditory cortex of the rat. ABR were obtained for each ear before noise exposure and 7 days after noise exposure, analyze change of the auditory threshold. Immunohistochemistry and the western blot was used to measure the change of PV in AC. At last, analyze the possible reason and mechanisms of those changes.Results(1)The mean and standard deviation of the left and right ear ABR thresholds was 20 ± 5d B. 7days post-exposure, the mean and standard deviation of the left and right ear ABR thresholds was 75 ± 5d B and 18.3±2.9d B, the left ear ABR thresholds were equivalently elevated compare to right ear(P<0.05). Statistically significant permanent threshold shifts were found compared to the pre-exposure values(P<0.05). While the right ear ABR thresholds no significant difference between pre-exposure and post-exposure(P>0.05). there is also no significant difference compare to controlgroup(P>0.05).(2) 7th day after noise exposure, The expression of PV in both AC in exposed increased significantly(p<0.05) compared with that in controls. Moreover, in the exposed rats, the expression of PV in the left AC also had a significant increase compared with that in right AC(p<0.05), however, there is no difference in the expression of PV between the left and right AC in controls.Conclusion 7th day after noise exposure,the left ear ABR thresholds was increase obviously, The expression of PV in both AC in exposed increased significantly compared with that in controls. In the test group, the expression of PV in the left AC also had a significant increase compared with that in right AC. These changes in expression of PV may suggest that possible interpretation may include their protective role against noise expose, a higher auditory-evoked metabolic activity, a increasing effect of excitatory inputs after noise-induced hearing impairment. This may be connected with tinnitus and auditory abnormality.