氟灭酸对豚鼠耳蜗螺旋动脉平滑肌细胞膜电位和兴奋性接头电位的作用

目的:观察氯通道阻断剂氟灭酸(NFA)对耳蜗螺旋动脉平滑肌细胞膜电位和电刺激血管周围交感神经纤维引起兴奋性接头电位(EJP)的影响。方法:在耳蜗螺旋动脉平滑肌离体标本上,运用细胞内微电极记录技术研究非甾体类抗炎药物对平滑肌细胞的作用。结果:100μmol/L NFA引起低静息膜电位平滑肌细胞产生了(14.7±4.4)mV的超极化反应,引起高静息膜电位平滑肌细胞仅产生了(1.4±0.8)mV的超极化反应(P<0.01)。NFA引起低静息膜电位平滑肌细胞的反应是浓度依赖性的,这一超极化反应能被钙激活钾通道的阻断剂北非蝎毒素(charybdotoxin)和iberiotoxin阻断。另外,在高静息膜电位的平滑肌细胞,NFA对刺激引起的平滑肌细胞EJP有更明显的抑制作用(P<0.01),但对低静息膜电位的平滑肌细胞引起的EJP作用不明显(P>0.05)。结论:NFA既能通过阻断钙激活的氯通道抑制平滑肌细胞产生的EJP,又能激活钙激活钾通道使平滑肌细胞产生超极化反应,表现出对平滑肌细胞作用的多样性。

Effect of Niflumic Acid on Membrane Potentials and Excitatory Junction Potential in Smooth Muscle Cells of Cochlear Spiral Modiolar Artery in Guinea Pigs

Objective: To explore the influence of niflumic acid(NFA,10-1 000 μmol/L,a Cl-channel antagonist,on the membrane potentials and excitatory junction potential(EJP) in smooth muscle cells(SMCs) of cochlear spiral modiolar artery(SMA) in guinea pigs.Methods: NFA induced responses on the acutely isolated SMA preparation were recorded by the intracellular recording technique.Results: Bath application of NFA could cause hyperpolarizations in all the low resting potential(RP) cells,but had little effect on high RP cells.In low and high RP SMCs,NFA 100 μmol/L caused hyperpolarizations of(14.7±4.4) mV and(1.4±0.8) mV(P<0.01),respectively.The NFA-induced responses were concentration-dependent in low RP SMCs.The hyperpolarization could be blocked by charybdotoxin and iberiotoxin.On the other hand,the majority of SMCs in vitro showed an EJP response to the transmural stimulation.NFA 100 μmol/L could not only notably inhibit the voltage but also shorten the time course of EJP in the high RP SMCs(P<0.01) while had little effect on the low RP SMCs(P>0.05).Conclusion: NFA not only induces concentration-dependent reversible hyperpolarizations via activation of the Ca2+-activated potassium channels,but also inhibits the EJP by blocking Ca2+-activated chloride conductance in SMCs of cochlear SMA.These findings suggest that NFA has a variety effect on SMCs.