水杨酸钠对大鼠耳蜗螺旋神经节细胞外向延迟整流钾电流及其尾电流的影响

The Effect of Sodium Salicylate on the IKDR and I_(K-tail) of Spiral Ganglion Neurons from Neonatal Rats

目的采用全细胞膜片钳技术记录耳蜗螺旋神经节细胞（spiral ganglion neurons,SGNs）外向整流钾电流及其尾电流,分析水杨酸钠对耳蜗SGNs外向整流钾电流及其尾电流的影响,初步探讨其耳毒性机制。方法采用全细胞膜片钳技术记录急性分离并进行细胞短时间（2-3 h）血清培养后,耳蜗SGNs外向延迟整流钾电流及其尾电流曲线,同时记录不同浓度水杨酸钠（0.01、0.1、0.5、1、10 mmol/L）对2种电流的影响。结果耳蜗SGNs上可记录到外向电流,该电流对4-氨基吡啶（4-AP）敏感,证明其为钾电流,该钾电流具有延迟整流特性;1 mmol/L水杨酸钠能明显抑制耳蜗SGNs外向延迟整流钾电流;＋50 mV的去极化电压刺激可使最大稳态电流幅值减少（46.3±2.0）%,水杨酸钠对此电流的抑制具有浓度依赖性,外液洗脱后耳蜗SGNs外向延迟整流钾电流可基本恢复正常。另外,可记录出耳蜗SGNs延迟整流钾电流的尾电流曲线;水杨酸钠可降低此尾电流峰值,并缩短尾电流的时间常数,加速尾电流的失活。结论钾电流在耳蜗SGNs正常电生理活动中有重要作用。水杨酸钠抑制耳蜗SGNs外向整流钾电流及其尾电流,并加速尾电流的失活,这种作用可导致耳蜗SGNs的电生理活动异常,从而引发水杨酸钠对听觉功能的损害。

Objective To investigate the effects of sodium salicylate on outward delayed rectifier potassium currents（IKDR ） and their tail currents（IK-tail）in isolated spiral ganglion neurons（SGNs）using patch-clamp technique and to inquire into the toxic mechanism. Methods After acute isolation and cell culture in serum for short time（2-3 h） ,the SGNs＇ curves of the IKDR and IK -tail were recorded using whole cell patch clamp technique. The effects of different concentrations of sodium salicylate（0.01, 0. 10,0.50,1.00,and 10.00 mmol/L）on the current curves of SGNs were observed. Results Because of its sensitivity to 4 AP, the outward current which could be recorded in SGNs was proved to be the potassium current（IK）. The IKDR could be inhibited with 1 mmol/L sodium salicylate obviously. The maximal magnitude of IKDR was decreased by（46.3±2.0）% after given the depolarized stimulation of ＋ 50 mV. Besides,the inhibitory effects of sodium salicylate on IKDR were concentration-dependent,and IKDR Of SGNs could mostly recover to its normal level after washed out. The curves of IK-tail in SGNs were recorded, and the peak of IK-tail and time constant were reduced,and deactivation was accelerated with sodium salicylate. Conclusion The IK played an important role in the normal electrophysiological activity of SGNs. But through inhibition of the IKDR and IK-tail and acceleration of IK-tail deactivation, sodium salicylate could induce the electrophysiological abnormality of SGNs to damage the acoustic function.