咪达唑仑对交感神经元N-型钙通道电流的影响

Effects of midazolam on N-type calcium currents of rat sympathetic neurons

目的 通过观察咪达唑仑对交感神经元全细胞N-型钙电流的影响,评价其对交感神经元的抑制作用。方法 用酶消化法获得急性分离的SD大鼠（7～10d）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（0.1、0.3、3.0、10、50、100μmol/L）对N型钙电流的影响。结果在钳制电位（Vh）-80mV,刺激电压（Vt）-30mV～+10mV条件下,不同浓度的咪达唑仑对N-型钙电流均有抑制作用,且呈浓度依赖性（r=0.964P<0.01）。临床相关浓度的咪达唑仑（0.3μmol/L）使钙通道电流峰值下降35％（P<0.01）。50％钙通道电流峰值受抑制时的咪达唑仑浓度（IC50）约为4.25μmol/L。结论 临床相关浓度的咪达唑仑对交感神经元全细胞N-型钙电流有明显的抑制作用,提示咪达唑仑的循环抑制作用可能与抑制交感神经系统的活动有关。

ve To investigate the effects of clinical relevant concentrations of midazolam on whole-cell N-type calcium currents of sympathetic ganglion neurons trying to assess the involvement of sympathetic ganglion in circulation depression produced by midazolam. Methods 7-10 d SD rats were decapitated and bilateral superior cervical ganglions were rapidly removed and kept in 4℃, oxygen saturated incubation solution. TTX 1μmol/L and nifedipine 10 μmol/L were added to the solution to block the Na+ and L-type calcium currents. Midazolam was also added to the solution. The final concentration of midazolam were 0.1, 0.3, 3, 10, 50, 100μmol/L.The effects of different concentration of midazolam on the whole-cell N-type calcium channel currents were assessed by patch-clamp technique. Results When the holding potential (Vh) was - 80mV and stimulating votage(Vt) was between - 30mV and 10mV midazolam inhibited the whole-cell N-type calcium currents dose-dependently ( r = 0.964, P < 0.01) . Clinical relevant concentration of midazolam (0.3μmol/L) reduced the peak currents by 35% (P< 0.01) and 10μmol/L midazolam reduced the peak values of I-V curve by 49% (P< 0.01) . The concentration required to produce 50% current inhibition was 4.25μmol/L.Conclusions Clinical relevant concentration of midazolam inhibits the whole-cell N-type calcium current significantly, indicating that the circulatory depression produced by midazolam may be related to the suppression of sympathetic activity.