金环蛇神经毒组分Ⅸ的研究

从金环蛇毒中分离得到一个作用于突触后膜的神经毒——组分Ⅸ。与通常的蛇毒突触后神经毒不同,组分Ⅸ对蛙腹直肌的乙酰胆碱量效曲线呈现非竞争性抑制。在有新斯的明存在时,高浓度乙酰胆碱使腹直肌产生相反的效应。在实验用浓度下,组分Ⅸ对¹²⁵Ⅱ标记的眼镜蛇神经毒与电鳐电器官膜碎片的结合无显著影响。应用电压固定技术的研究表明,组分Ⅸ能够抑制终板电流,最后使其完全消失,且能缩短终板电流的半衰期。增加衰减速率常数α值;对终板电流的平衡电位无显著影响.实验提示组分Ⅸ是通过乙酰胆碱受体以外的作用方式产生阻断作用的,作用部位可能在终板离子通道。

STUDIES OF THE NEUROTOXIN FRACTION IX FROM BUNGARUS FASCIATUS VENOM

A postsynaptic neurotoxin—Fraction Ⅸ was Separated from the venom of Bungarus fasciatus. Fraction Ⅸ was different from other postsynaptic neurotoxins in its blocking manner. Fraction Ⅸ non-competitively inhibited the concentration-response curve of acetylcholine on frog abdominal rectus muscle; neostigmine could not completely antagonize the effects of Fraction Ⅸ, On the contrary, under higher agonist concentration range, the muscle relaxed progressively with increasing agonist concentration. Under the experimental conditions, Fraction Ⅸ did not modify the binding of ¹²⁵Ⅰ-cobrotoxin to the membrane preparation from the electric organ of Narcine maculata which is rich in nicotinic acetylcholine receptors. Under the effect of Fraction Ⅸ, the endplate current (EPC) of frog sartorius muscle was inhibited and disappeared eventually. Fraction Ⅸ showed some effect on the time course of EPC: the EPC half decay time (T_1/2)was shortened, EPC decay rate constant (α) was increased. However, the EPC equilibrium potential was not changed by Fraction Ⅸ. Based on these data, it was suggested that Fraction Ⅸ may act on endplate ion channels and result in neuronluscular blockage.