咪达唑仑对交感神经元电压门控性钾电流的影响

目的: 观察不同浓度咪达唑仑对交感神经元电压门控钾通道电流的影响, 探讨临床浓度咪达唑仑对钾电流的作用是否与抑制交感神经系统有关。方法: 用酶消化法获得急性分离的SD 大鼠(7 ~ 10 d) 颈上交感神经节细胞, 应用膜片钳技术记录不同浓度的咪达唑仑对电压门控钾电流的影响。结果: 在钳制电位(Vh)-80 mV, 刺激电压(Vt)^-100 mV ~ 30 mV, 时程160 ms 条件下, 不同浓度的咪达唑仑对电压门控钾电流均有抑制作用, 且呈浓度依赖性。临床相关浓度的咪达唑仑(0.3 μmol·L^-1) 使钾通道电流峰值下降3.89 %(P =0.88) 。50 %钾通道电流峰值受抑制时的咪达唑仑浓度(IC₅₀) 约为70.06 μmol·L^-1 。结论: 咪达唑仑对交感神经元电压门控钾电流具浓度依赖性抑制作用, 但临床浓度咪达唑仑对钾电流影响较小。

Effects of midazolam on macroscopic voltage-gated potassium currents in rat sympathetic neurons

AIM: To explore the influence of different concentration midazolam on the macroscopic voltage-gated potassium currents and to discuss the relationship between potassium currents andinhibitory effect of clinical relevant concentration midazolam on sympathetic nervous system.METHODS: Superior sympathetic ganglion neurons were dissociated enzymatically from 7 to10-day-old rat.Experiments were performed about 5 h after plating atroom temperature (20-24 ℃).Appropriate solution was chosen to separate the K⁺ current from the other transmembrane currents.1 μmol·L^-1 TTX was applied to the extracelluar solution to block the Na + current.Midazolam was also resolvedin extracelluar solution to get various concentration (0.1, 0.3, 3, 10, 50, 100 μmol·L^-1).Currents were recorded with the patch-clamp technique in whole cell configuration using glass electrodes with a tip resistance of 2-4 M.Potassium currents were evoked by test pulse from^-100 mV to +30 mV with holding potential-80mV. Data were analyzed using Clampfit 6.0 and Oringih 5.0 software.Whole-cell current records were corrected for leakage and capacitance by using the P/5 protocol.RESULTS: Midazolam dose-dependently inhibited the wholecell potassium currents.Clinical relevant concentrationmidazolam (0.3 μmol·L^-1) only reduced the peak currents by 3.89 %(P =0.88).The concentration required to produce 50 %current inhibition(IC₅₀) was 76.065 μmol·L^-1.CONCLUSION: Midazolam inhibits the whole-cell potassium current significantly and dose-dependently, but clinical relevant concentration midazolam has minor effect on the potassium currents, indicating that the inhibitory effect of midazolam on potassium current is not related to the suppression of activity of sympathetic system.