Expression Of Neurotrophins And The Receptors In The Cochleas And Inferior Colliculus In The Aged Rats

IntroductionAlthough the mechanisms of presbyacusis are still unclear, apoptosis in theauditory system have been implicated as contributing to presbyacusis. And at presentmany experiments focus the neurotrophins correlated with auditory.Theexperiment is to investigate the correlation between neurotrophins and presbyacusisthrough studying expression of neurotrophins and the receptors in thecochleas and inferior colliculus in the aged rats.So as to get study informationof presbycusis and to provide the reference data and theory basis of the investigation onthe etiology, prophylaxis and clinical treatment of presbycusis.Material and MethodsThe expressions were quantitated by quantitation Real Time PCR and located byimmunohistochemical analysis. The aged Wister rats were divided into different groupsby auditory brainstem responses (ABRs). The animals were intraperitoneallyadministered sodium pentobarbital gentamicin 30-40 mg/kg.Under the dissecting microscope, inner ear tissues were removed and fixed for afurther 4 hours at 4°C by immersion in the same fresh fixative. The tissues were rinsedfirst in PBS (pH 7.4) at 4°C, cryoprotected in PBS (pH 7.4) containing 10% sucrose for4 hours and then in PBS (pH 7.4) containing 30% sucrose overnight at 4°C, embeddedin OCT compound, before being rapidly frozen in liquid nitrogen. The frozen sections(10 um thick) were cut on a cryostat (Miles), and mounted onto glass slides. The slideswere air-dried and stored at -20°C until they were examined immunohistochemically.Total 8 cochleas were prepared for the analysis of.Result Qualification of Real Time PCR show the expression andimmunohistochemistry of BDNF was obviously decreased while those of itshigh-affinity receptor trk B, NT3 and its high-affinity receptor trk C were nosignificantly difference in the cochleas in the aged rats with presbycusis. And theexpressions of BDNF and NT3 were statistically no significance while thoseof trk B and trk C were up-regulated in the inferior colliculus in the aged rats withpresbycusis. Interestingly, the expression of p75 was obviously increasedin the aged rats with presbycusis and the difference as compared to its normal controlwas significant.Discussion The study of correlation of apoptosis with the mechanisms of presbyacusis is paidmore and more attention to, but it is unclear. After all, the etiology is a complicatedchange in the level of genes. The experiment is to investigate the correlation betweenneurotrophins and presbyacusis through studying expression of neurotrophins and thereceptors in the cochleas and inferior colliculus in the aged rats.So as to get studyinformation of presbycusis and to provide the reference data and theory basis of theinvestigation on the etiology, prophylaxis and clinical treatment of presbycusis. Our results show the expression and immunohistochemistry of p75, a high-affinityreceptor, was obviously increased in the aged rats with presbycusis and the differenceas compared to its normal control was significant. The reson is unknown, but it ispresumed that it is closely related to the mechanism of presbyacusis. The low-affinity neurotrophin receptor p75 (p75NTR) is a member of the tumor...