Theeffectofearlyauditorydeprivationontheage-dependentexpressionpatternofNR2BmRNAinratauditorycortexCaixiaBi,YileiCui,YutingMao,JinghongXu,FengXu,JipingZhang,XindeSun*ResearchCentreforBrainScience,EastChinaNormalUniversity,Shanghai200062,ChinaAbstractUsinginsituhybridization(ISH),presentresearchminutelyinvestigatedtheage-dependentexpressionpatternofNR2BmRNAinratauditorycortex(AC)duringpostnataldevelopmentandtheeffectofearlyauditorydeprivation.Fortheratsinthenormalgroup,themRNAexpressionofNR2Bwashighestatbirth(postnatalday1),butdeclinedrapidlyuntillowlevelofadulthood,duringwhichtherewasarisingperiodwithatransientpeakonpostnatalday21(P21);fortheratsinthedeprivedgroup,thewholedeclining-as-agingtrendofNR2BmRNAexpressionwassimilartothatofnormalgroup,buttheexpressionlevelfromP15toP27weremuchlowerthanthatofnormalgroupwiththegreatestreductionfromP21toP23andthetransientpeakonP21disappeared.Inbothgroups,thedistributionpatternofNR2BmRNApositiveneuronsin6layersanddorsal,medialandventralsub-districtsofauditorycortexwasalsoexamined.Thereisnosignificanteffectontheexpressionpatternbetweennormalanddeprivedgroup.Ourresultsindicatedthattheearlyauditorydeprivationdecreasedtheage-dependentexpressionpatternofNR2BmRNA,suggestingthatNR2Bmayplayanimportantroleinthedevelopmentalplasticityofauditoryfunctioninrats.Keywords:AuditoryCortex;AuditoryDeprivation;Insituhybridization(ISH);NR2BmRNAExpression1.IntroductionDuringasensitiveperiodinpostnataldays,animalsshowaformofexperience-dependentdevelopmentplasticityincentralnervoussystem.IthasbeenproposedthattheN-methyl-D-asparate(NMDA)receptorplayacrucialroleduringthiscriticalperiod.Withage,thechangesofNMDARfunctionmayberelatedtothevarietyofthesubunitcomposition,whichincludetheNR2BandNR2A[30,40].Intheneocortex,theNMDAreceptoriscomposedofNR1andNR2subunits.NR2AandNR2B,thetwoNR2subunitshaveattractedfocusesrespectively.SomeresearchproposedthatNR2BmightpromoteplasticitymorethandoestheNR2Asubunit[41,43,44].NakanishihavedemonstratedthatmRNAencodingNR2Bwashighlyexpressedthroughouttheforebrain,withespeciallyhighlevelsintheolfactorybulbs,hippocampus,andcortex.Levelswereundetectableinthepons-medullaandcerebellum[32].In﹡Correspondingauthor.XindeSunE-mail:xdsun@bio.ecnu.edu.cnseveralareasofcerebellumandbrainstemtheexpressionleveldecreasedrapidlyin7daysafterhttp://www.paper.edu.cn1thepeak,andhadbeenundetectablesincepostnatalday28[1,5,29].Thedetectionofproteinhasreachedthesimilarconclusion[4],showingthediversepostnatalexpressionmodelofNR2B.Invisualcortex,NR2Bsubunitshavebeenfoundmaintainingthehighlevelsatbirththroughoutandbeyondthecriticalperiod[38],increasinggradually[34,35],ortransientlydecliningattheendofthecriticalperiod[4,5].However,ithasbeenarguedthatthecriticalfactormaybeanincreaseintheNR2A/NR2Bratio,ratherthattheamountsofthesubunits[7,11,17,34,35,38].SensoryexperiencealsodifferentiallyregulatesNR2AandNR2Bsynapticexpression.IthasbeendemonstratedthatearlyvisualexperienceregulatedtheexpressionoftheNR2A(butnottheNR2B)subunitinmammalvisualcortex[8,34,35],however,thestudyonbirds’lMANshowsNR2Bsubunitmightplaymorecrucialroleduringcriticalperiod[3,41].DevelopmentalchangesofNR2BmRNAandproteinlevelhavebeeninvestigatedintherat[20,30,37,40,45,47],however,thesesresearcheshavenotconcentratedontheauditorycortexandespeciallythecriticalperiod.Hsieh’sworkonNMDAsubunitdohasstud...
