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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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Citing This Article：

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).