庭院蜗牛神经元对注入钙离子的敏感性。

The sensitivity of Helix aspersa neurones to injected calcium ions.

Meech R W

J Physiol. 1974 Mar;237(2):259-77. doi: 10.1113/jphysiol.1974.sp010481.

Abstract

When calcium chloride was injected into Helix aspersa neurones there was a fall in membrane resistance and the membrane potential became hyperpolarized.2. The reversal potential of the response was dependent on the concentration of potassium in the external solution.3. Injection of a calcium-EGTA buffer containing 9 x 10(-7)M free calcium reduced the membrane resistance by 25%. When calcium chloride was injected it was necessary to increase the total intracellular calcium concentration by about 10(-3)M to produce similar change of resistance.4. In sodium-free (Tris) solution there was a slow fall of membrane resistance as if the intracellular calcium concentration had increased. There was a similar resistance change in the presence of 2,4-dinitrophenol and iodoacetate.5. A series of repetitive depolarizing pulses produced a long lasting reduction in membrane resistance which was enhanced by 2,4-dinitrophenol and iodoacetate.6. It is concluded that (a) injection of calcium causes an increase in potassium permeability, (b) the injected calcium is rapidly pumped from the cytoplasm by a sodium-dependent mechanism and by mitochondria, and (c) 1-2 msec depolarizing pulses stimulate an influx of calcium. This influx is rapid enough to trigger potassium activation during an action potential.

摘要

向玛瑙螺神经元注射氯化钙时，膜电阻下降，膜电位超极化。
反应的逆转电位取决于细胞外溶液中钾的浓度。
注射含9×10⁻⁷M游离钙的钙-乙二醇双四乙酸缓冲液使膜电阻降低25%。注射氯化钙时，需要将细胞内总钙浓度提高约10⁻³M才能产生类似的电阻变化。
在无钠（Tris）溶液中，膜电阻缓慢下降，就好像细胞内钙浓度增加了一样。在2,4-二硝基苯酚和碘乙酸存在的情况下也有类似的电阻变化。
一系列重复性去极化脉冲使膜电阻产生持久降低，2,4-二硝基苯酚和碘乙酸可增强这种降低。
得出以下结论：（a）注射钙会导致钾通透性增加；（b）注入的钙通过钠依赖性机制和线粒体从细胞质中迅速泵出；（c）1-2毫秒的去极化脉冲刺激钙内流。这种内流速度足够快，足以在动作电位期间触发钾的激活。