Study On Salicylate-induced Excitotoxicity Of Spiral Ganglion Neurons:the Effects Of NMDA Receptor Activity On GABAa Receptor Currents

Objective To observe the effect of NMDAR on GABAaR current under the sodium salicylate on rat spiral ganglion neurons(SGN),to further improve the receptor mechanism of sodium salicylate ototoxicity.Methods SGN was isolated from newborn SD rats,Using the whole cell patch clamp recording mode to observe the effect of activating or inhibiting NMDAR on GABAaR current under different concentrations of sodium salicylate(SS).Results(1)The morphological characteristics of SGN: SGN is round or oval,the volume is large,the surface is smooth,the membrane is complete and the refractivity is strong,The halation around the cells is obvious,the cytoplasm is uniform and the nucleolus are large.After 6 hours,it adhered gradually and adhered completely about 7 hours,After 24 hours,the neurite outgrowth from the SGN soma was more than three times that of the soma and crossed into net,7 days later,SGN began to atrophy and apoptosis,and the cell lysed and released cytoplasm.(2)SGN identification: If an acute isolated and cultured cell could be recorded an inward current of rapid activation and rapid inactivation.The current could be rapidly blocked by 0.3 u M TTX.After elution,the inward current could be basically recovered,this approved the current is a TTX sensitive voltage gated sodium channel current,the cell is confirmed as SGN.(3)Under physiological condition,0.5mM SS and 5mM SS respectively,No current has been induced by 0.5mM NMDA(below the same).(4)Under the action of 0.5mM SS and 5mM SS,the average current density induced by 0.5mM(following the same)GABA was decreased by 28.47%(n=5,F=67.020,P=0.000<0.05)and 55.77%(n=6,F=67.020,P=0.000<0.05)respectively.(5)compared with GABA alone,the average current density induced by 0.5mM(following the same)NMDA+GABA and 0.2mM(following the same)APV+GABA was decreased by 11.12%(n=5,F=1.626,P=0.098>0.05)and 6.64%(n=5,F=1.626,P=0.306>0.05)respectively.(6)compared with 0.5 mM SS +GABA,the average current density induced by 0.5mM SS+GABA+NMDA was decreased by 27.72%(n=5,F=11.779,P=0.021<0.05),the average current density induced by 0.5mM SS+GABA+APV was increased 22.30%(n=5,F=11.779,P=0.048<0.05).(7)compared with 5 mM SS +GABA,the average current density induced by 5mM SS+GABA+NMDA was decreased by 23.09%(n=8,F=162.313,P=0.007<0.05),the average current density induced by 5mM SS+GABA+APV was increased 115.08%(n=5,F=162.313,P=0.000<0.05).Conclusions(1)Sodium salicylate reversibly inhibited the current of GABAaR and was concentration dependent.(2)NMDAR has no significant effect on GABAaR current Under physiological condition.(3)Under the sodium salicylate,NMDAR inhibited the current of GABAaR and was concentration dependent.that is,the higher the concentration of sodium salicylate,the stronger the inhibitory effect of NMDAR on the GABAaR current.