罗比卡因对脊髓背角神经元钠电流特性的影响

The effects of ropivacaine on the sodium channel in dorsal horn neurons

目的 探讨酰胺类新局麻药罗比卡因对脊髓神经阻滞作用的机制。方法 以全细胞膜片钳技术记录罗比卡因对急性分离新生ＳＤ 鼠（０～７ ｄ） 脊髓背角神经元钠电流的影响。结果 在电压钳的状态下（钳制电压Ｖｈ８０ ｍ Ｖ，刺激电压Ｖｔ０ ｍ Ｖ），罗比卡因（１０～４００ μｍｏｌ） 对钠电流有抑制作用，且呈浓度依赖性，其ＩＣ５０ 为１１７ ．３２ μｍｏｌ，明显高于相同电压钳条件下布比卡因的ＩＣ５０（５３ ．７０１ μｍｏｌ） ；罗比卡因对钠电流的抑制具有电压依赖性。当Ｖｈ －６０ ｍ Ｖ，Ｖｔ０ ｍＶ 时，其ＩＣ５０ 为７４ ．２８ μｍｏｌ，明显低于罗比卡因在电压钳Ｖｈ － ８０ ｍ Ｖ，Ｖｔ０ ｍ Ｖ 条件下的ＩＣ５０（１１７．３２ μｍｏｌ）；罗比卡因对钠电流的抑制具有频率依赖性，重复刺激（５ Ｈｚ，２０ ｍｓ） 可增加罗比卡因的抑制作用；罗比卡因不影响钠电流的激活曲线，但可使钠电流的稳态失活曲线产生超极化移动（１１ ｍ Ｖ）。结论 应用全细胞膜片钳技术，罗比卡因对背角神经元钠电流有抑制作用，且呈电压和浓度依赖性，其抑制效力弱于布比卡因；罗比卡因优先作用于钠通道电流的失活状态。

Objective To study the effects of ropivacaine on the sodium channel in rat dorsal horn neurons. Methods Whole cell patch clamp techniques were used.Results Under voltage clamp, ropivacaine(10～400 μmol) produced a dose dependent inhibition of sodium current. From a holding potentia (V h) of -80mV, sodium currents evoked by test pulses to 0 mV were inhibited by ropivacaine with a mean IC 50 value of 117.32 μmol, which was more than that value of the bupivacaine (IC 50 53.701 μmol). The inhibition effect of ropivacaine was also voltage dependent. Current evoked from a V h of -60 mV was inhibited by ropivacaine with a mean IC 50 value of 74.28 μmol, which was less than that obtained at the V h of -80 mV. The inhibition effect of ropivacaine on sodium current was use dependent. Repeated activation by a train of depolarizing pulses (5 Hz,20 ms) increased the inhibitory effects of ropivacaine, the ratios, of amplitudes of the 20th to the 1st pulse were 91.17% and 71.11% in the absence and presence of ropivacaine (50 μmol) respectively. Ropivacaine also produced a significant hyperpolarizing shift of 11 mV in the steady state inactivation curve of sodium current. Conclusion Using the whole cell patch technique, ropivacaine is voltage and use dependent inhibitor of sodium current in the dorsal horn neurons; It preferentially acts on the steady state inactivation of the sodium channel.(Shanghai Med J, 2000,23∶11 13)