Jaffe D B, Johnston D, Lasser-Ross N, Lisman J E, Miyakawa H, Ross W N
Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030.
Nature. 1992 May 21;357(6375):244-6. doi: 10.1038/357244a0.
The dendrites of many types of neurons contain voltage-dependent Na+ and Ca2+ conductances that generate action potentials (see ref. 1 for review). The function of these spikes is not well understood, but the Ca2+ entry stimulated by spikes probably affects Ca(2+)-dependent processes in dendrites. These include synaptic plasticity, cytotoxicity and exocytosis. Several lines of evidence suggest that dendritic spikes occur within subregions of the dendrites. To study the mechanism that govern the spread of spikes in the dendrites of hippocampal pyramidal cells, we imaged Ca2+ entry with Fura-2 (ref. 9) and Na+ entry with a newly developed Na(+)-sensitive dye. Our results indicate that Ca2+ entry into dendrites is triggered by Na+ spikes that actively invade the dendrites. The restricted spatial distribution of Ca2+ entry seems to depend on the spread of Na+ spikes in the dendrites, rather than on a limited distribution of Ca2+ channels. In addition, we have observed an activity-dependent process that modulates the invasion of spikes into the dendrites and progressively restricts Ca2+ entry to more proximal dendritic regions.
许多类型神经元的树突含有电压依赖性钠通道和钙通道，这些通道可产生动作电位（综述见参考文献1）。这些尖峰的功能尚未完全明了，但尖峰刺激引起的钙内流可能会影响树突中依赖钙的过程。这些过程包括突触可塑性、细胞毒性和胞吐作用。有几条证据表明树突尖峰出现在树突的亚区域内。为了研究控制海马锥体细胞树突中尖峰传播的机制，我们用Fura-2成像钙内流（参考文献9），并用一种新开发的钠敏感染料成像钠内流。我们的结果表明，钙进入树突是由主动侵入树突的钠尖峰触发的。钙内流受限的空间分布似乎取决于钠尖峰在树突中的传播，而不是取决于钙通道的有限分布。此外，我们观察到一个活动依赖过程，该过程调节尖峰侵入树突，并逐渐将钙内流限制在更靠近树突近端的区域。
