石杉碱甲对兔肌肉功能的影响和治疗实验性重症肌无力的效果

Effect of huperzine A on the function of skeletal muscle and it's efficacy in treating experimental autoimmune myasthemia gravis (EAMG) in rabbits

麻醉兔在体坐骨神经-腓肠肌、正中神经-旋前圆肌制备实验表明:正常兔累积iv Hup-A使腓肠肌单收缩平均增强50％的同时,功能性收缩-强直收缩平均抑制约20％,肌肉电位也受部分阻断。但对EAMG兔,iv Hup-A 25μg/kg能明显增强和改善其病态肌肉的电位和收缩功能,并能对抗d-TC所引起的阻断。

Huperzine A (Hup-A,i.e.fordine)is a new alkaloid isolated from Huperziaceae plant Phlegmariurus fordii or Huperzia serrata.It is a reversible ChE inhibitor exhibiting selective inhibition on AChE.In this paper we experimented with Hup-A on sciatic-gastrocnemius and median nerve-pronator teres preparations in anesthetized rabbits.The results indicated that Hup-A caused more obvious changes in stimulation-evoked cortracticas of gattrocne-mius than those in action potentials of the muscle.By calculating from the cumulative dose-response carves,it was obtained that cumulative iv Hup-A 76.5μg/kg produced 50% increase of amplitude of twitch,but meanwhile it decreased the amplitude of tetanus induced by repetitive stimulation of 50 and 100/s by 20% and the D5 value of twitch by-30.3%.The action potentials ofboth gastrocnemius and pronator teres showed repetitive firing at stimulation with single pulse and were partially blocked during repetitive stimulation of 50 and 100/s.While EAMG rabbits were treated with iv Hup-A 25μg/ kg,the contractile function and action potentials of their morbid muscles were potentiated and improved obviously.This dose of the drug also effectively antagonized the reurcmuscular blocking action caused by tubocurarine in EAMG rabbits.In addtion it should be emphasized that one of the most important indexes of efficacy to treat a MG or EAMG with this type of drug is potenti-ation of tetanus rather than twitch.