Expression Of GABA_A Receptors Subunits In The Cochleas And Inferior Colliculus In The Postnatal Rats

IntroductionWith the progress of the investigation on the etiology, prophylaxis andclinical treatment of non-genetic congenital profound deafness, the laws ofdevelopment in the auditory system, especially during the developmentalsensitive period, are paid more and more attention. And the relations betweenthe inhibitory GABAergic system and the auditory have been studied by someresearchers oversea, but the distribution, subunits and role of the GABAAreceptor and its functions and significance during the early developmentalperiod is unclear in the auditory system..Now it is obvious that the cochlea is the peripheroceptor and inferiorcolliculus is the key exchange station through the auditory way. And GABAis the main inhibitory neurotransmitter not only in the vertebrate centralneural system but also in the cochlea and IC. And one of its receptors GABAAreceptor is present in them. Although the effects of cochlear lesion onplasticity of the auditory central system during the cochlea developmentalsensitive period have been explored, the results are different due to thedifferent subjects and different auditory deprivation methods in the differentexperiments. To investigate the cause of the different results and explore theexpression rules of GABAAR subunits in the cochleas and IC in the ratsduring the cochlea developmental sensitive period and also to investigate theinfluence of early auditory deprivation on the receptor, two gentamicinototoxic animal models were developed in the newborn rat: the cochleas inone group were thoroughly ruined, and another just softly damaged. Using 9吉林大学博士学位论文RT-PCR and in situ hybridization, the expression rules of GABAAR 2 and2 subunits in the cochleas and I C in postnatal rats during the earlydevelopmental period, so as to get study information of synaptic plasticityand to provide the reference data and theory basis of the investigation on theetiology, prophylaxis and clinical treatment of non-genetic congenitalprofound deafness.Material and MethodsThe adult Wister rats were divided into two groups: group I:experimental group, group II: controls. The newborn rats were divided intothree experimental groups and accordingly the other three control groups:experimental groups animals were intraperitoneally administered dailygentamicin 80 mg/kg respectively from P1to P8,P7to P16,another groupanimals were administered once gentamicin 200 mg/kg in P9. [1-4]Hearingloss was evaluated by the pinna reflex and by click-evoked auditorybrainstem responses (ABRs). And the adult Wister rats were intraperitoneallyadministered daily gentamicin 80 mg/kg for eight days.The animal models were evaluated by ABRs and scanning electronmicroscope(SEM). And the expressions were quantitated by half quantitationPT-PCR and located by in situ hybridization. The PCR were done using thespecial primers of GABAAR 2and 2 subunits together with interior controlGAPDH. The gray scales of the electrophoresis products of PCR wereobserved and analyzed under ultraviolet analytical system. In situhybridization were done by non-radioactivity oligonucleotide probe and resultswere observed by light microscope. 10吉林大学博士学位论文ResultsABRs were recorded in all the animals to evaluate the hearing thresholds.The responses were obtained at the higher thresholds in the experimental groupadministered gentamicin from P7 to P16 and its control group. And thedifference between them is significant.No peaks could be identified atintensities as high as 110 dB SPL at P16 given gentamicin at P9.SEM showed that no obviously difference between the group givengentamicin from P1 to P7 and its control group, the same in the adult group.The results in the group administered gentamicin at P9 demonstrated thatsevere lesions of the organ of Corti, affecting similarly each turn of thecochlea. The complete loss of the inner and outer hair cells was observed.There were no cuticular plate of IHCs and OH...