Edwards C, Dolezal V, Tucek S, Zemková H, Vyskocil F
Proc Natl Acad Sci U S A. 1985 May;82(10):3514-8. doi: 10.1073/pnas.82.10.3514.
Experiments were performed to investigate the effects on the spontaneous, nonquantal release of acetylcholine (AcCho) from motor nerve terminals of substances known to inhibit the AcCho transport system present in cholinergic synaptic vesicles. In mouse diaphragms, the hyperpolarization normally produced by d-tubocurarine in the endplate area of muscle fibers that had been treated by an anticholinesterase was partly or completely blocked by 2-(4-phenylpiperidino)cyclohexanol (AH5183, 0.1-1 microM), quinacrine (0.1 microM), and tetraphenylborate (1 microM). Since the sensitivity of the subsynaptic area to AcCho was not changed, the block of the hyperpolarizing action of d-tubocurarine indicated in inhibition of the spontaneous, nonquantal release of AcCho. This was confirmed in experiments on rat diaphragm using direct radioenzymatic measurement of the AcCho released into the incubation medium. The release of AcCho from the innervated diaphragm was decreased by about 50% in the presence of AH5183 (0.01-1 microM) and by 42% in the presence of quinacrine (0.1-1 microM). The AcCho released was presumably neural, since the release of AcCho from 4-day denervated diaphragms was not diminished by either AH5183 or quinacrine. The results indicate that the spontaneous release of AcCho from the motor nerve terminals is highly sensitive to low concentrations of specific inhibitors and is probably mediated by a carrier. It is proposed that spontaneous release is due to the incorporation into the membrane of the nerve terminal during exocytosis of the vesicular transport system responsible for moving AcCho into the vesicle.
进行了实验以研究已知抑制胆碱能突触小泡中乙酰胆碱（AcCho）转运系统的物质对运动神经末梢乙酰胆碱自发、非量子释放的影响。在小鼠膈神经膈肌标本中，抗胆碱酯酶处理过的肌纤维终板区，d -筒箭毒碱通常引起的超极化，部分或完全被2 -（4 -苯基哌啶基）环己醇（AH5183，0.1 - 1微摩尔）、奎纳克林（0.1微摩尔）和四苯硼酸盐（1微摩尔）阻断。由于突触下区域对AcCho的敏感性未改变，d -筒箭毒碱超极化作用的阻断表明AcCho的自发、非量子释放受到抑制。这在大鼠膈神经膈肌标本实验中得到证实，采用直接放射酶法测量释放到孵育介质中的AcCho。在AH5183（0.01 - 1微摩尔）存在时，受神经支配的膈肌中AcCho的释放减少约50%，在奎纳克林（0.1 - 1微摩尔）存在时减少42%。释放的AcCho大概来自神经，因为AH5183或奎纳克林都不会减少去神经4天的膈肌中AcCho的释放。结果表明，运动神经末梢AcCho的自发释放对低浓度的特定抑制剂高度敏感，可能由载体介导。有人提出，自发释放是由于在将AcCho转运到小泡中的小泡转运系统胞吐过程中，其掺入神经末梢膜所致。
