Changes Of Auditory Threshold And Expression Of Glutamate Decarboxylase-67in The Auditory Cortex In Rats Following Noise Exposure

Objective To observe the auditory brainstem response and number of glutamatedecarboxylase-67(GAD67) positive neurons in auditory cortex of rats pre-andpost-exposure to noise, and study changes of auditory threshold and expressionof GAD67following noise exposure.Methods21rats were randomly divided into control group and exposed group.The rats of exposed group were exposed to above4kHz,100dB SPL white noisefor2hours to gain animal models of noise exposed, then measured auditorybrainstem response immediately, and at the7th and14th day post-exposure,and marked GAD67-positive neurons in auditory cortex with immunohistochemicaltechniques, compared the GAD67-positive neurons amount of exposed group tothe control.Results1）The auditory threshold for clicks of all rats exposed to noise showedan initial threshold shift, returned to near control levels at the14th day.2) GAD67-positive neurons at0day post-exposure (78.76±16.11/mm2) increasedby105%than the control group (P <0.01), Then, at the7th and14th day inexposed group were significantly lower than the control group (P <0.05).Conclusion Exposure to above4kHz,100dB SPL white noise for2hours affectedthe rats on auditory function, with a temporary threshold shift. The number of GAD67-positive neurons increased first followed by a decline to belowcontrol levels, which may be closely related to noise deafness and other seriesof dysfunction.