IDENTIFICATION OF IONIC CURRENTS AT PRESYNAPTIC NERVE-ENDINGS OF THE LIZARD
IDENTIFICATION OF IONIC CURRENTS AT PRESYNAPTIC NERVE-ENDINGS OF THE LIZARD
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DOI：
10.1113/jphysiol.1989.sp017684
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发表时间：
1989-07-01
影响因子：
5.5
通讯作者：
MOORE, JW
中科院分区：
文献类型：
--
作者：
LINDGREN, CA;MOORE, JW
1.在运动神经末梢沿着的几个位置，用一个局灶性细胞外电极测量了与动作电位侵入蜥蜴运动神经末梢相关的离子电流。2.这些实验观察到的电流可以与计算机模拟的动作电位传播到神经末梢相匹配。他们发现，虽然Na+通道是半结中的主要离子电流通路，但K+通道提供了末端分支和终扣中的主要通路。3.突触前末梢的钙电流被四乙基铵（TEA）所掩蔽。该电流被以下物质阻断：（a）镉，（B）ω-芋螺毒素GVIA和（c）硝苯地平，但不受浓度小于或等于100 μ M的镍的影响。当用TEA预处理使动作电位的持续时间大大延长时，硝苯地平的作用变得更加明确。Bay K 8644的效果不一致。4.发射器释放，测量突触后电流，有药理学反应的概况类似的钙离子电流，除了发射器释放增加可靠和可逆的湾K 8644。5.这种药理学反应特征与Fox、Nowycky和Tsien（1987 a）在鸡背根神经节神经元中鉴定的L型Ca 2+通道相同。我们没有看到证据表明蜥蜴运动神经末梢中有一种以上的钙通道。6.应用延迟整流钾通道阻断剂3，4-二氨基吡啶（DAP）可显示钙激活的钾电流IK（Ca）。此K（Ca）电流被TEA、Charybdotoxin和用钴替代细胞外钙离子所阻断。
1. Ionic currents associated with the invasion of an action potential into the motor nerve ending of the lizard, Anolis-carolinensis, were measured with a focal extracellular electrode at several locations along the nerve ending. 2. These experimentally observed currents could be matched with computer simulations of action potential propagation into the nerve ending. They revealed that while Na+ channels are the major ionic current pathway in the heminode, K+ channels provide the major pathway in the terminal branches and boutons. 3. Calcium current in the presynaptic ending was unmasked by the applciation of tetraethylammonium (TEA). This current was blocked by: (a) cadmium, (b) .omega.-conotoxin GVIA and (c) nifedipine, but was unaffected by nickel at concentrations less than or equal to 100 .mu.M. Nifedipine''s action became more definitive when the duration of the action potential was greatly extended by pre-treatment with TEA. The effect of Bay K 8644 was inconsistent. 4. Transmitter release, as measured by postsynaptic current, had a pharmacological response profile similar to that of the Ca2+ current, with the exception that transmitter release was increased reliably and reversibly by Bay K 8644. 5. This pharmacological response profile is identical to that of the L type Ca2+ channel identified by Fox, Nowycky and Tsien (1987a) in chick dorsal root ganglion neurones. We saw no evidence for more than a single type of Ca2+ channel in lizard motor nerve endings. 6. A calcium-activated K+ current IK(Ca) was revealed by application of 3,4-diaminopyridine (DAP), a delayed-rectifier K+ channel blocker. This K(Ca) current was blocked by TEA, charybdotoxin and by substitution of cobalt for extracellular calcium.