简介：TheGermanwaltzingguineapigisastrainofanimalsexpressingdeafnessandseverebalancedisordersatbirth.ThemutationarosespontaneouslyinabreedingfacilityinGermanyandastheaffectedanimalsshowacharacteristicwaltzingbehavior,thestrainisnamedtheGermanwaltzingguineapig.ThestrainispresentlybredonlyatKarolinskaInstitutet.Thehereditaryinnerearimpairmenthasarecessivemodeofinheritanceandthestrainthusproducesnotonlyaffectedhomozygotesbutalsosymptom-freeheterozygotesandfullynormaloffspring.Theoutcomedependssolelyonthegenotypeoftheparents.Theheterozygotes,whichhaveobtainedthe'waltzing'genefromoneparentonly,havenormalhearingandnobalancedysfunction.Theheterozygousanimalsappearnormalbutwill,inturn,carrythegeneticdefecttothenextgeneration.Thepresentthesisisfocusedontheseanimals.Noiseandototoxicdrugsarewellknownstressfactorsthatinterferenegativelywiththehearingorganinbothhumansandanimals,causinghearingimpairment.However,theinter-individualvariabilityinsusceptibilitytoauditorystressfactorsissurprisinglylarge,mostlikelyduetodifferentgeneticpredisposition.Inthisstudy,heterozygousanimalsoftheGermanwaltzingguineapig,animalscarryingageneticdefectknowntocauseseverehearingimpairment,wereusedtostudyhowanunexploredgenefordeafnessinteractswithauditorystressagents,i.e.noiseexposureandtheototoxicdrugsgentamicinandcisplatin.AnimalswereexposedtobothnarrowbandaswellasbroadbandnoiseatdifferentagesandhearingthresholdsweremeasuredusingABRs.HeterozygotesoftheGermanwaltzingguineapigshowedlessthresholdshiftscomparedtocontrolstrains.Olderanimalswerelessaffectedbythenoisetraumathanyoungeranimals.Totestthehypothesisthattheefferentsystemcontributestoprotectionoftheinnerearagainstnoisetrauma,measurementsusinganewmethodofpostonsetadaptationofDPOAEsandmaximumadaptationmagnitudewereconducted.T