Mechanism of disturbed nerve conduction : analysis of ionic permeability of single myelinated nerve fiber using vaserine-gap voltage clamp technique

(1)在分离的大鼠单个有髓神经纤维上，用凡士林间隙电压钳技术检测抗GM1抗体的致病作用。用GM1神经节苷脂免疫兔，获得抗GM1抗血清。细胞外应用无补体活性的抗GM1抗血清可增加K电流的上升率和幅度，而对Na电流的影响不大。在活性补体存在的情况下，抗GM1抗体使钠电流降低，并引起非特异性漏电流进行性增加。结果表明，抗GM1抗体可在结旁区发现K~+通道，抗体-补体复合体可阻断Na~+通道，破坏Ranvier膜。(2)观察高糖、脂肪酸和酮体对神经纤维的影响。外用D-葡萄糖后，当葡萄糖浓度高于30 mM时，动作电位和钠电流均出现幅度降低，且L-葡萄糖的作用大于D-葡萄糖。应用20 mM乙酰乙酸乙酯后，内向Na~+电流减少，下射电流明显增加。加入20 mM 3-羟基丁酸后，Na电流减小，K~+电流增大。这些结果提示，高糖和酮体通过影响有髓神经纤维的电生理活动，在神经功能障碍的发生发展中起重要作用。

(1) The pathogenic role of anti-GM1 antibody was examined using the vaseline-gap voltage clamp technique on isolated single myelinated rat nerve fibers. Anti-GM1 antisera were obtained from rabbits immunized with GM1 ganglioside. Extracellularly applied anti-GM1 antisera without complement activity increased both the rate of rise and the amplitude of the K+ current elicited with little affect on Na current. In the presence of active complement, anti-GM1 antibodies decreased the Na current, and caused a progressive increase of non-specific leakage current. The results indicate that anti-GM1 antibodies can uncover K^+ channels in the paranodal region and antibody-complement complexes may block Na^+ channels and disrupts the membrane at the Ranvier.(2) The effect of high glucose, fatty acids and ketone bodies on nerve fibers was examined. After external application of D-glucose, action potential and Na^+ current reduced in amplitude at the concentration of glucose higher than 30 mM.The effect of L-glucose was greater than that of D-glucose. After application of 20mM acetoacetic acid, inward Na^+ current decreased and undershoot markedly increased. The application of 20mM 3-hydroxybutyric acid induced a decrease of Na+ current and an increase of K^+ current. These results suggest that high glucose and ketone bodies play important roles in the development of nerve dysfunction by affecting electrophysiological activity of myelinated nerve fibers.