Smith J E, Clark A W, Kuster T A
J Neurocytol. 1977 Oct;6(5):519-39. doi: 10.1007/BF01205217.
Frog neuromuscular junctions were treated with both concentrated black widow spider venom (BWSV) and elevated extracellular calcium (5-50 mM). This procedure causes a dramatic increase in the frequency of spontaneous miniature endplate potentials (mepps) which persists for only a few minutes. In contrast, BWSV-induced mepp activity, the venom effect (VE), continues for 20 min-1 h at junctions in elevated calcium Ringer solutions treated with doses of dilute venom or at junctions in normal calcium (1.91 mM) Ringer solution treated with concentrated venom. Following the disappearance of the VE in elevated extracellular calcium, only a few normal amplitude mepps and a few giant amplitude mepps are observed. The disappearance of the VE in these preparations is irreversible and occurs whether exposure to elevated extracellular calcium precedes or follows exposure to BWSV. Electron microscopy indicates that the major structural alterations produced by exposure to concentrated BWSV and 20 mM calcium Ringer solution are the swelling of nerve terminal mitochondria and the clumping of synaptic vesicles, large numbers of which remain in the terminals. Exposure to 20 mM calcium Ringer solution alone produces no ultrastructural modifications in these preparations. These observations can best be explained if one of the effects of BWSV is to increase the permeability of the nerve terminal membrane to calcium. Only doses of concentrated venom can sufficiently elevate intracellular calcium to a concentration at which synaptic vesicles clump together, thus interruping the transmitter release process.
用浓缩的黑寡妇蜘蛛毒液（BWSV）和升高的细胞外钙（5 - 50 mM）处理青蛙神经肌肉接头。此操作会使自发微小终板电位（mepps）的频率急剧增加，且这种增加仅持续几分钟。相比之下，在高钙任氏液中用稀释毒液处理的接头处或在正常钙（1.91 mM）任氏液中用浓缩毒液处理的接头处，BWSV诱导的mepp活性，即毒液效应（VE），会持续20分钟至1小时。在细胞外钙升高后VE消失后，仅观察到少数正常幅度的mepps和少数大幅度的mepps。这些制剂中VE的消失是不可逆的，无论在暴露于BWSV之前还是之后暴露于升高的细胞外钙，都会发生这种情况。电子显微镜显示，暴露于浓缩的BWSV和20 mM钙任氏液所产生的主要结构改变是神经末梢线粒体肿胀和突触小泡聚集，其中大量突触小泡仍留在末梢。单独暴露于20 mM钙任氏液不会在这些制剂中产生超微结构改变。如果BWSV的作用之一是增加神经末梢膜对钙的通透性，那么这些观察结果就能得到最好的解释。只有浓缩毒液的剂量才能将细胞内钙充分升高到使突触小泡聚集在一起的浓度，从而中断递质释放过程。
