BLOCKING AND ISOLATION OF A CALCIUM-CHANNEL FROM NEURONS IN MAMMALS AND CEPHALOPODS UTILIZING A TOXIN FRACTION (FTX) FROM FUNNEL-WEB SPIDER POISON
BLOCKING AND ISOLATION OF A CALCIUM-CHANNEL FROM NEURONS IN MAMMALS AND CEPHALOPODS UTILIZING A TOXIN FRACTION (FTX) FROM FUNNEL-WEB SPIDER POISON
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DOI：
10.1073/pnas.86.5.1689
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发表时间：
1989-03-01
影响因子：
11.1
通讯作者：
CHERKSEY, B
中科院分区：
文献类型：
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作者：
LLINAS, R;SUGIMORI, M;CHERKSEY, B
一种来源于漏斗网蜘蛛毒素（FTX）的Ca ~（2+）通道阻断剂，使得对哺乳动物浦肯野细胞神经元和鱿鱼巨突触前末梢Ca ~（2+）传导的离子通道的定义和研究成为可能。在小脑切片中，FTX阻断浦肯野细胞中的Ca 2+依赖性锋电位，减少潜在超极化后的锋电位，并增加Na+依赖性平台电位。在鱿鱼巨突触中，FTX阻断突触传递而不影响突触前动作电位。突触前电压钳结果显示内向钙电流和递质释放的阻断。FTX用于分离来自小脑和鱿鱼视叶的通道。将分离的产物掺入黑色脂质膜中，并通过使用膜片钳技术进行分析。小脑通道在80 mM Ba ~（2+）中电导为10- 12 pS，在100 mM Ca ~（2+）中电导为5-8 pS，具有电压依赖性开放概率和动力学。在通道的细胞质侧的高Ba 2+浓度将平均开放时间从1至3毫秒增加到1秒以上。在鱿鱼视叶中也分离到了类似的通道。但在Ba ~（2+）存在下，其电导率较高，最大开放概率约为小脑组织的一半，且对高浓度的胞浆Ba ~（2+）敏感。两个通道都被FTX、Cd 2+和Co2+阻断，但不被ω-阻断。芋螺毒素或二氢吡啶类。这些结果表明，在哺乳动物神经元和鱿鱼preterminal的主要Ca 2+电导之一，代表了一个以前未定义的类的Ca 2+通道的激活。我们建议，它被称为“P”通道，因为它是第一次在浦肯野细胞中描述。
A Ca2+-channel blocker derived from funnel-web spider toxin (FTX) has made it possible to define and study the ionic channels responsible for the Ca2+ conductance in mammalian Purkinje cell neurons and the preterminal in squid giant synapse. In cerebellar slices, FTX blocked Ca2+-dependent spikes in Purkinje cells, reduced the spike after potential hyperpolarization, and increased the Na+-dependent plateau potential. In the squid giant synapse, FTX blocked synaptic transmission without affecting the presynaptic action potential. Presynaptic voltage-clamp results show blockage of the inward Ca2+ current and of transmitter release. FTX was used to isolate channels from cerebellum and squid optic lobe. The isolated product was incorporated into black lipid membranes and was analyzed by using patch-clamp techniques. The channel from cerebellum exhibited a 10- to 12-pS conductance in 80 mM Ba2+ and 5-8 pS in 100 mM Ca2+ with voltage-dependent open probabilities and kinetics. High Ba2+ concentrations at the cytoplasmic side of the channel increased the average open time from 1 to 3 msec to more than 1 sec. A similar channel was also isolated from squid optic lobe. However, its conductance was higher in Ba2+, and the maximum opening probability was about half of that derived from cerebellar tissue and also was sensitive to high cytoplasmic Ba2+. Both channels were blocked by FTX, Cd2+, and Co2+ but were not blocked by .omega.-conotoxin or dihydropyridines. These results suggest that one of the main Ca2+ conductances in mammalian neurons and in the squid preterminal represents the activation of a previously undefined class of Ca2+ channel. We propose that it be termed the "P" channel, as it was first described in Purkinje cells.