Linder T M
J Gen Physiol. 1973 Jan;61(1):56-73. doi: 10.1085/jgp.61.1.56.
The closer muscle of the crab, Chionoecetes, has at least two classes of excitatory neuromuscular synapses. In one class of synapses an action potential depolarizing the synaptic region releases much more transmitter if it has been preceded recently by another action potential. The other class of synapses shows this property, called facilitation, to a far lesser extent. Immediately after one conditioning stimulus the level of facilitation is similar in both classes. The rate of the ensuing decay of the facilitation is the critical factor differentiating the two classes of synapses. The relationship between external Ca(++) concentration and transmitter release is similar for both classes of synapses. The slope of a double logarithmic plot of this relationship varies from 3.1 between 5 and 10 mM Ca(++) to 0.9 between 30 and 40 mM Ca(++). Facilitation does not significantly change when tested in external Ca(++) concentrations ranging from 7 to 30 mM. The extracellularly recorded nerve terminal action potential does not increase in amplitude during facilitation. The results suggest that the mechanism of synaptic facilitation is similar for both classes of synapses and occurs after the stage in transmitter release involving Ca(++).
雪蟹（Chionoecetes）的闭合肌至少有两类兴奋性神经肌肉突触。在一类突触中，如果突触区域去极化的动作电位之前最近有另一个动作电位，则会释放更多的递质。另一类突触在远小得多的程度上表现出这种称为易化的特性。在一次条件刺激之后，两类突触的易化水平立即相似。随后易化衰减的速率是区分这两类突触的关键因素。两类突触的外部钙离子（Ca(++)）浓度与递质释放之间的关系相似。这种关系的双对数图的斜率在5至10 mM钙离子浓度之间为3.1，在30至40 mM钙离子浓度之间为0.9。在7至30 mM的外部钙离子浓度下进行测试时，易化没有显著变化。在易化过程中，细胞外记录的神经末梢动作电位的幅度没有增加。结果表明，两类突触的突触易化机制相似，且发生在涉及钙离子的递质释放阶段之后。
