南湖霉素对神经肌肉传递的影响和机理探讨

EFFECT OF NANHUMYCIN ON NEUROMUSCULAR TRANSMISSION AND ITS MECHANISM

南湖霉素(Nanhumycin,NHM)是我国学者筛选的一个新的多醚类抗生素,具有抑制枯草杆菌生长和抗鸡球虫病的作用。本工作利用电生理胞内记录方法,在小鼠隔神经膈肌标本上观察了它的作用,结果为:(1)NHM不可逆地阻遏神经肌肉传递,20 μg/ml时1.5—2 h完全阻遏。(2)2—20μg/ml浓度的NHM引起小终板电位发放频率显著地和阵发性地升高,持续40—60min;其间,终板电位的平均量子含量也相应升高,并随传递阻遏的发生,终板电位完全消失。(3)NHM进行性和不可逆地降低肌细胞的静息膜电位。(4)NHM对膜的去极化及增加小终板电位发放频率的作用在无Na^+溶液中基本上不再出现。Na^+通道阻断剂河豚毒不影响NHM的作用。这些结果都可以用NHM是一种阳离子载运体,Na^+载体,来解释。

Nanhumycin (NHM) is a new polyether antibiotic, which suppresses the growth ofBacillus subtilis and shows an anticoccidial effect. By means of intracellular recordingtechnique, the effects of NHM on mouse phrenic nerve--diaphragm preparations wereobserved. The main results are as follows: (1)20 μg/ml NHM irreversibly blocked neu-romuscular transmission in 1.5--2.0 h. (2) 2--20 μg/ml NHM evoked a drastic andspasmodic increase of the frequency of miniature endplate potentials (MEPPs) and a si-multaneous increase of the mean quantal content of endplate potentials for 40--60min, which was followed by complete blockage of EPPs. (3) NHM decreased the rest-ing potential (RP) of muscle cells progressively and irreversibly. (4) NHM's effects onRP or MEPP disappeared in Na^+-free physiological solution but persisted in the pres-ence of tetrodotoxin (TTX). All these results support the notion that NHM is a cationionophore, Na^+ carrier.