Competitive calcium binding: Implications for dendritic calcium signaling
Competitive calcium binding: Implications for dendritic calcium signaling
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DOI：
10.1023/a:1008891229546
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发表时间：
1998-07-01
影响因子：
1.2
通讯作者：
Helmchen, F
中科院分区：
文献类型：
--
作者：
Markram, H;Roth, A;Helmchen, F
在生理温度下，动作电位诱发新皮层锥体神经元树突中的钙瞬变，时间常数< 100 ms。该时间段可能不足以使流入的钙离子与所有存在的Ca 2+结合分子平衡。因此，我们探讨了非平衡动力学的Ca 2+结合到众多的Ca 2+反应伴侣内的树突状隔室使用数值模拟。在短暂的Ca 2+内流后，具有最快Ca 2+结合动力学的反应伴侣最初结合的Ca 2+比从化学平衡预测的要多，而伴随反应伴侣结合的较少。另一方面，在重复钙电流脉冲或在较慢的Ca 2+流入期间，较慢的反应伴侣有效地结合Ca 2+。非平衡Ca 2+分布可以进一步提高通过战略布局的反应伙伴在车厢内。使用Ca 2+缓冲EGTA作为竞争对手的荧光-3，我们证明竞争性的钙离子结合内树突实验。非平衡钙动力学提出了一个潜在的机制差异和条件激活的树突状细胞内的目标。
Action potentials evoke calcium transients in dendrites of neocortical pyramidal neurons with time constants of < 100 ms at physiological temperature. This time period may not be sufficient for inflowing calcium ions to equilibrate with all present Ca2+-binding molecules. We therefore explored nonequilibrium dynamics of Ca2+ binding to numerous Ca2+ reaction partners within a dendritelike compartment using numerical simulations. After a brief Ca2+ influx, the reaction partner with the fastest Ca2+ binding kinetics initially binds more Ca2+ than predicted from chemical equilibrium, while companion reaction partners bind less. This difference is consolidated and may result in bypassing of slow reaction partners if a Ca2+ clearance mechanism is active. On the other hand, slower reaction partners effectively bind Ca2+ during repetitive calcium current pulses or during slower Ca2+ influx. Nonequilibrium Ca2+ distribution can further be enhanced through strategic placement of the reaction partners within the compartment. Using the Ca2+ buffer EGTA as a competitor of fluo-3, we demonstrate competitive Ca2+ binding within dendrites experimentally. Nonequilibrium calcium dynamics is proposed as a potential mechanism for differential and conditional activation of intradendritic targets.