Korkotian Eduard, Holcman David, Segal Menahem
Department of Neurobiology, The Weizmann Institute, Rehovot 76100, Israel.
Eur J Neurosci. 2004 Nov;20(10):2649-63. doi: 10.1111/j.1460-9568.2004.03691.x.
We investigated the role of dendritic spine morphology in spine-dendrite calcium communication using novel experimental and theoretical approaches. A transient rise in [Ca2+]i was produced in individual spine heads of Fluo-4-loaded cultured hippocampal neurons by flash photolysis of caged calcium. Following flash photolysis in the spine head, a delayed [Ca2+]i transient was detected in the parent dendrites of only short, but not long, spines. Delayed elevated fluorescence in the dendrite of the short spines was also seen with a membrane-bound fluorophore and fluorescence recovery from bleaching of a calcium-bound fluorophore had a much slower kinetics, indicating that the dendritic fluorescence change reflects a genuine diffusion of free [Ca2+]i from the spine head to the parent dendrite. Calcium diffusion between spine head and the parent dendrite was regulated by calcium stores as well as by a Na-Ca exchanger. Spine length varied with the recent history of the [Ca2+]i variations in the spine, such that small numbers of calcium transients resulted in elongation of spines whereas large numbers of calcium transients caused shrinkage of the spines. Consequently, spine elongation resulted in a complete isolation of the spine from the dendrite, while shrinkage caused an enhanced coupling with the parent dendrite. These studies highlight a dynamically regulated coupling between a dendritic spine head and its parent dendrite.
我们使用新颖的实验和理论方法，研究了树突棘形态在棘-树突钙信号传导中的作用。通过对笼锁钙进行闪光光解，在装载了Fluo-4的培养海马神经元的单个棘头中产生了[Ca2+]i的瞬时升高。在棘头进行闪光光解后，仅在短棘而非长棘的母树突中检测到延迟的[Ca2+]i瞬时变化。使用膜结合荧光团也观察到短棘树突中延迟的荧光升高，并且钙结合荧光团漂白后的荧光恢复动力学要慢得多，这表明树突荧光变化反映了游离[Ca2+]i从棘头到母树突的真正扩散。棘头与母树突之间的钙扩散受钙库以及钠钙交换器的调节。棘的长度随棘中[Ca2+]i变化的近期历史而变化，使得少量的钙瞬变导致棘伸长，而大量的钙瞬变则导致棘收缩。因此，棘伸长导致棘与树突完全隔离，而收缩则导致与母树突的耦合增强。这些研究突出了树突棘头与其母树突之间动态调节的耦合。
