The sodium salicylate affects the expression of NMDA receptor and GABAa receptor subunits in spiral ganglion neurons of the cochlea through DA receptor

Abstract

Objective:To investigate mRNA expression of dopamine receptor subtypes in the rat cochlear spiral ganglion neurons (SGN) following exposure to the sodium salicylate. In addition, we observed the effect of sodium salicylate on N methyl-D-aspartic acid (NMDA) receptor subunit NR1 and gamma aminobutyric acid (GABA)a receptor subunit GABRα2 mRNA under the circumstance of DR activation or blocking. Moreover, we also focused on the the interaction between receptors mediated by SS.Method:Immunofluorescence techniques were applied to detect DR (DR1 and DR2) expression in cultured rat SGN. Moreover, RT-PCR was performed to assess NR1 and GABRα2 subunit mRNA.Result:Immunofluorescence images showed co-localization of DR1/DR2 and βⅢ-tubulin protein in SGN bodies and axons. RT-PCR results illustrated that ①DR subtypes of DRd1-5 were detected in the SGN. ②The mRNA expression of all subtypes of DR and GABRα2, NR1 subunits were obviously upregulated except DRd3 after treatment with sodium salicylate. Among them, DRd1 expression increased 34.64%(t=-5.123,P=0.007),DRd2 expression increased 34.60%(t=-5.206,P=0.006),DRd4 expression increased 20.87%(t=-3.337,P=0.029),DRd5 expression increased 26.42%(t=-6.054,P=0.004),GABRα2 expression increased 30.41%(t=-2.839,P=0.047),NR1 expression increased 39.22%(t=-6.243,P=0.003).③After exposure to sodium salicylate (5 mmol/L), dopamine (100 μmol/L), DR1 agonist (SKF38393,20 μmol/L), DR2 agonist (Quinpirole,20 μmol/L), GABRα2 expression increased 21.78%,27.45%,33.02%,33.42% respectively (F=12.399,P=0.001),and NR1 expression increased 28.70%,26.82%,29.03%,35.05%(F=50.395,P=0.000) respectively.④Compared with the group of sodium salicylate treatment alone, both sodium salicylate + DR1 antagonist (SCH23390,20 μmol/L) group and sodium salicylate + DR2 antagonists (Eticlopride,20 μmol/L) group had a suppression on GABRα2 and NR1 mRNA expression.GABRα2 mRNA reduced 29.56%,37.10%(F=22.101,P=0.000) and NR1 mRNA expression decreased 37.62%,32.83% respectively(F=72.933,P=0.000).Conclusion:Most of the DR subtypes mRNA expression in SGN were increased following exposure to sodium salicylate. DR may be involved in the effect of sodium salicylate on GABAaR and NMDAR mRNA expression.