Eflects of ions onthe stimulation-induced changas in transmitten veleace at the frog neuromusculan junction.

刺激引起的神经递质释放变化的四个组成部分被称为青蛙神经肌肉接头的突触可塑性。这些是：快速和缓慢的促进，增强和增强，根据重复神经刺激后的衰减时间常数分类。大多数实验支持快速易化是由残余Ca^<2+>引起的观点。但是，其他三个组成部分的原因尚不清楚。我研究了Mg^<2+>和其他二价阳离子对这三种成分的电生理作用。通过终板电位（EPP）的振幅和微型终板电位（MEPP）的频率估计递质释放。神经刺激引起的递质释放的增加被描述为四个分量的乘积。在高浓度Mg^<2+>时，强直刺激（100 Hz，5000次）后MEPP频率的增强幅度显著增加。相反，在高Mg^<2+>林格氏液中，增强幅度（MEPP频率和EPP振幅）降低。Ni^<2+>促进增强幅度，Sr^<2+>增强慢易化.

Four components of stimulation-induced changes in neurotransmitter release are known as the synaptic plasticity at the frog neuromuscular junction. These are : fast and slow facilitation, augmentation and potentiation, classified by their decay time constants after repetitive nerve stimulation. Most experiments support the view that fast facilitation is caused by residual Ca^<2+>. However, the causes of the other three components are not clear. I have studied electrophysiologically the effect of Mg^<2+>and other divalent cations on these three components. Transmitter release was estimated by the amplitudes of endplate potential (EPP) and by the frequencies of miniature endplate potential (MEPP). The increase in the transmitter release by nerve stimulation is described as the product of four components. The magnitude of potentiation of MEPP frequencies after a tetanic nerve stimulation (100Hz, 5000times) increased markedly in high Mg^<2+>concentrations. Conversely, the magnitude of augmentation (MEPP frequencies and EPP amplitude) decreased in the higher Mg^<2+>Ringer solution. Ni^<2+> promoted the amplitude of potentiation and Sr^<2+> enhanced slow facilitation.