Expression of GIiaI FibriIIary Acidic Protein and Changes of Auditory during CriticaI Period of DeveIopment in the Auditory Cortex in Rats / 听力学及言语疾病杂志

ABSTRACT

Objective To study changes of auditory brainstem evoked potentials (ABR)and the expression of glial fibrillary acidic protein (GFAP)during the critical period of the development of the auditory cortex in rats. Methods Fifty Sprague - Dawley (SD)rat pups were divided into five groups(n=10 per group)postnatal 14 days group,postnatal 21 days group,postnatal 28 days group,postnatal 35 days group and postnatal 42 days group.The rats were decapitated after the evaluation of ABR.The auditory cortex was taken and immunohisto-chemical staining was used to detect the expression of GFAP in rat auditory cortex in each group.The protein ex-pressions of GFAP in rat auditory cortex in each group were tested by western blot methods respectively.ResuIts The ABR thresholds gradually decreased along with the increasing days after the birth.The average ABR thresholds in postnatal 14 days group,postnatal 21 days group,postnatal 28 days group,postnatal 35 days group and postnatal 42 days group were (84.5 ± 4.97)dB SPL ,(70.5±3.69)dB SPL ,(58.5±5.80)dB SPL,(37.0±4.83)dB SPL and(35.5±3.69)dB SPL,respectively.There were no significant differences in ABR thresholds between the postnatal 35 days group and the postnatal 42 days group (P>0.05),whereas,significant differences were found among the other groups(P<0.05 or P<0.01.GFAP expression in auditory cortex gradually increased in all five groups.The average integrated optical density (IOD)of postnatal 14 days group,postnatal 21 days group,postnatal 28 days group,postnatal 35 days group and postnatal 42 days group were 474.36±234.56,1465.93 ±474.96,2163.06 ± 353.36,6572.01±808.88 and 7244.37±932.90,respectively.The differences among all five groups were statisti-cally significant (P<0.05 orP<0.01 ).The protein levels of GFAP in the auditory cortex of postnatal 14 days group,postnatal 21 days group,postnatal 28 days group,postnatal 35 days group and postnatal 42 days group were 1.00±0.06,3.07±0.07,4.92±0.05,6.88±0.03 and 8.92±0.04.The differences among all five groups were sta-tistically significant (P<0.05).ConcIusion The ABR threshold gradually decreased and GFAP expression in audi-tory cortex gradually increased from postnatal 14 days to postnatal 42 days ,suggesting that astrocytes may promote the development and maturation of the auditory cortex and the auditory central system in rats.