The Observation Of The Effect Of Glutamate On The Cultured Spiral Ganglion Cells Of The Post-natal Mouse Cochlea

Objectives Some previous studies have indicated that sensorineural deafness caused by noise, ischemia, hypoxia, infection and ototoxicity drugs are all companied with nerve cells damage directly or indirectly. And those cells damage is closely related to glutamate's accumulation in the cochlea. Glutamate is an afferent nerve transmitter. This study is to observe the damage induced by the glutamate to the spiral ganglion cells in vitro, and initially explore the mechanism of the damage, which willprovide a proof for the prevention and treatment of sensorineural deafness.Methods Newborn to 1-day postnatal BALB/C mouse pups were killed. The spiral ganglion cells (SGCs) were removed to culture in vitro. Glutamate, as a direct mediator in different concentration was used in the study. Apoptosis of the SGCs was observed by Hoechst33258 staining and DNA ladder. Semi-quantitative RT-PCR was applied to observe the expression of BCL-2 gene. Densitometry was carried out by using the Image Master VDS3.0 image analysis system, and BCL-2 signal density was compared with the correspondingβ-actin density. Datas were presented as means±SD and statistics were done by SPSS for windows.Results Hoechst33258 staining and DNA ladder showed apoptotic phenomenon. The apoptotic cells of the SGCs treated by different concentration of glutamate were 13±2.2353(0μmol/L), 48.3333±4.2147(100μmol/L), 100.3333±9.1352(200μmol/L), 179.3333±16.2235(500μmol/L), 236.6667±24 (1000μmol/L), respectively. The apoptotic rate of the SGCs increased significantly at glutamate concentration of 100μmol/L, compared with the control (P＜0.05). These results indicated that the celluar viability of the SGCs was decreased significantly, and the apoptotic rate of the SGCs was increased significantly by glutamate. The expression of Bcl-2 gene was up-regulated higher as the increase of the concentration of glutamate in the cultured SGCs, and the expression of Bcl-2 gene was up-regulated significantly at concentration of gulutamate≥100μmol/L.Conclusions Glutamate can induce excitotoxic damage of the SGCs. The damage became serious as the glutamate concentration increased. RT-PCR showed that glutamate results in up-regulating the expression of the Bcl-2 gene. This expression also related to the glutamate concentration.