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乙酞胆碱对蛇运动神经末梢离子通道活动的反馈调节

顾深, 施玉棵

(中国科学院上海生理研究所，上海200031)

摘要

由研究乙酞胆碱受体激动剂和阻断剂的作用提出，在脊椎动物运动神经末梢存在着对乙酞胆碱(ACh )释放的反馈调节。神经末梢的离子通道在递质释放中有重要作用。是利用周膜下记录技术，研究ACh对蛇运动神经末梢离子通道调节作用的报告。(1) 2 mmol/L ACh明显抑制依钙K~(+)流(I_(K)(Ca)，此效应与3 mmol/L TEA的相似。由于nAChR激动剂尼古丁(2 mmol/L)不影响IK,f和1K, Ca，阿托品对ACh抑制I_(K)_(f)和I_(K)_(Ca)的作用无影响，提示上述作用是由阿托品不敏感的mAChR介导的。(2) ACh对钙流(IC.)的调控。由30 mmol/L TEA暴露的1_(ca)在加入2mmol压ACh后时程缩短，升高溶液中Ca~(2+)浓度(至7 mmol/L)后此效应更加明显，作用是可逆的。对同时加入TEA (30 mmol/L)和3, 4-DAP (300 umol/L)阻断全部K+通道所暴露的Ca平台，ACh有明显抑制作用。2 mmol/L的阿托品可部分逆转这种效应。由这些结果推测，在正常情况下ACh通过抑制I_(g)_(f),，和I_(K)_(a)。促进ACh释放，实行正反馈调节;而在Ic。异常增大时，ACh通过抑制IC.，抑制ACh释放，实行负反馈调节。

关键词： 乙酞胆碱; 反馈调节; 运动神经末梢; 钾通道; 钙通道; 蛇

FEEDBACK REGULATION OF ACETYLCHOLINE (ACh) ON ION CHANNEL ACTIVITY IN SNAKE MOTOR NERVE TERMINALS

GU CHEN , SHI YU-LIANG

(Shanghai Institute of Physiology, Chinese Academy of Sciences, Shanghai 200031)

Abstract

In the vertebrate motor nerve terminals，the fact that the ACh release was affected by various activators and blockers of ACh receptors suggests the existence of several types of feedback regulation. The regulatory effect of ACh on the various ion channels in the snake motor nerve terminals was investigated by using subendothelial recording technique.(1)Suppression of IKcca>. Similar to that of 3 mmol/L TEA，IK(cB) could also be reversibly suppressed by 2 mmol/L ACh. (2) Regulatory effect on Ic, The time course of Ica in the presence of 30 mmol/ L TEA was decreased by perfusion of 2
mmol/L ACh，an effect being more clear in high [Ca ~(2+〕。(7 mmol/L).The Ca~(2+)plateau，revealed by further addition of 3，4-DAP (300 }tmol/L) to block all K~(+)channels，was also inhibited. These inhibitory effects could be reversed by 2 mmol/L atropine. It is likely that the inhibition of I_(K)_(f)and IK(ca) by ACh is to improve ACh release in normal condition，suggesting the presence of a positive feedback mechanism，while
under circumstances in which lca is increased，ACh may inhibit I_(c)_(a) so as to suppress the release itself as a result of negative feedback mechanism.

Key words: acetylcholine;feedback regulation;motor nerve terminal;Potassium channel;calciumhannel;snake

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引用本文：

顾深, 施玉棵. 乙酞胆碱对蛇运动神经末梢离子通道活动的反馈调节[J]. 生理学报 1996; 48 (6): .

GU CHEN , SHI YU-LIANG. FEEDBACK REGULATION OF ACETYLCHOLINE (ACh) ON ION CHANNEL ACTIVITY IN SNAKE MOTOR NERVE TERMINALS . Acta Physiol Sin 1996; 48 (6): (in Chinese with English abstract).