Empty synaptic vesicles recycle and undergo exocytosis at vesamicol-treated motor nerve terminals

作     者：Parsons, RL Calupca, MA Merriam, LA Prior, C 

作者机构：Univ Vermont Coll Med Dept Anat & Neurobiol Burlington VT 05405 USA Univ Strathclyde Dept Physiol & Pharmacol Strathclyde Inst Biomed Sci Glasgow G4 0NR Lanark Scotland 

出 版 物：《JOURNAL OF NEUROPHYSIOLOGY》 (神经生理学杂志)

年 卷 期：1999年第81卷第6期

页      面：2696-2700页

核心收录：

学科分类：0710[理学-生物学] 1001[医学-基础医学(可授医学、理学学位)] 07[理学] 071003[理学-生理学] 

基　　金：NINDS NIH HHS [NS-23978] Funding Source: Medline 

主　　题：乙酰胆碱/代谢 载体蛋白质类/拮抗剂和抑制剂 游蛇科 电刺激 胞吐作用 荧光染料 膜转运蛋白质类 运动神经肌肉终板/药物作用 运动神经肌肉终板/生理学 运动神经元/药物作用 神经末梢/药物作用 哌啶类/药理学 吡啶鎓化合物 季胺类化合物 突触膜/药物作用 突触膜/生理学 突触小泡/药物作用 突触小泡/代谢 囊泡乙酰胆碱转运蛋白质类 膜泡运输蛋白质类 动物 

摘      要：Empty synaptic vesicles recycle and undergo exocytosis at vesamicol-treated motor nerve terminals. J. Neurophysiol,. 81: 2696-2700, 1999. We investigated whether recycled cholinergic synaptic vesicles, which were not refilled with ACh, would join other synaptic vesicles in the readily releasable store near active zones, dock, and continue to undergo exocytosis during prolonged stimulation. Snake nerve-muscle preparations were treated with 5 mu M vesamicol to inhibit the vesicular ACh transporter and then were exposed to an elevated potassium solution, 35 mM potassium propionate (35 KP), to release all preformed quanta of ACh. At vesamicol-treated endplates, miniature endplate current (MEPC) frequency increased initially from 0.4 to 300 s(-1) in 35 KP but then declined to 1 s(-1) by 90 min. The decrease in frequency was not accompanied by a decrease in MEPC average amplitude, Nerve terminals accumulated the activity-dependent dye FM1-43 when exposed to the dye for the final 6 min of a 120-min exposure to 35 KP. Thus synaptic membrane endocytosis continued at a high rate, although MEPCs occurred infrequently. After a 120-min exposure in 35 KP, nerve terminals accumulated FM1-43 and then destained, confirming that exocytosis also still occurred at a high rate. These results demonstrate that recycled cholinergic synaptic vesicles that were not refilled with ACh continued to dock and undergo exocytosis after membrane retrieval. Thus transport of ACh into recycled cholinergic vesicles is not a requirement for repeated cycles of exocytosis and retrieval of synaptic vesicle membrane during prolonged stimulation of motor nerve terminals.