Depolarization and calcium entry in squid giant axons

作者：P. F. Baker, Alan Lloyd Hodgkin, E B Ridgway · 发表于：The Journal of Physiology · 年份：1971 · DOI：10.1113/jphysiol.1971.sp009641 · 被引用次数：730 · 研究领域：bioluminescence and chemiluminescence research、Photoreceptor and optogenetics research、Neuroscience and Neural Engineering

1. Changes in ionized calcium in giant axons were followed by recording the light produced by injected aequorin.2. From the effect of injecting calcium buffers the internal concentration of ionized calcium was found to be about the same as in a mixture of 45 Ca EGTA:55 free EGTA, i.e. about 0.3 muM.3. After an axon had been exposed to cyanide for 50-100 min the velocity of the aequorin reaction increased about 500 times. This effect, which could be reversed rapidly by removing cyanide, was probably brought about by release of calcium from an internal store.4. Injecting 30 mumole ATP per litre of axoplasm into a cyanide-poisoned axon caused a transient lowering of light intensity; oligomycin blocked the effect.5. Raising external calcium or replacing external sodium by choline or lithium reversibly increased the light produced by axons injected with aequorin.6. Stimulation at 50-200 impulses/sec in a solution containing 112 mM-Ca caused the light intensity to increase to a new steady level; after stimulation the light intensity returned to its original level with a time constant of 10-30 sec. Similar but smaller effects were seen in solutions containing less external calcium. The recovery after stimulation is probably due to uptake of calcium by the internal store.7. Injecting 3 m-mole EGTA per litre axoplasm lowered the resting glow and abolished the aequorin response to stimulation.8. There was no light response to stimulation immediately after an axial injection of aequorin...