Nicholson C
Fed Proc. 1980 Apr;39(5):1519-23.
Changes in [Ca2+]0 are known to affect axonal excitability and synaptic transmission. Ca2+ is also a major component of dendritic action potentials, and changes in [Ca2+]0 may therefore influence dendritic function. Use of the Ca2+-specific ion-selective microelectrode has shown that significant decreases in [Ca2+]0 occur in stimulated neuronal ensembles. Such changes are greatly enhanced during spreading depression and anoxia. The changes appear to be the result of Ca2+ entry into cells during activity, since the diffusion characteristics of Ca2+ in the extracellular space are not unusual. Decreases in [Ca2+]0 would lower the threshold for neuronal excitability but reduce synaptic transmission; rough numerical estimates of these effects are compiled. These are sufficiently large under some conditions to suggest, but not prove, possible modulatory effects of changes in [Ca2+]0. Variation in [Ca2+]0, however, is seen to be a valuable indicator of Ca2+-mediated processes in the nervous system.
已知细胞外钙离子浓度（[Ca2+]0）的变化会影响轴突兴奋性和突触传递。钙离子也是树突动作电位的主要成分，因此[Ca2+]0的变化可能会影响树突功能。使用钙离子特异性离子选择性微电极已表明，在受刺激的神经元群体中，[Ca2+]0会显著降低。在扩散性抑制和缺氧期间，这种变化会大大增强。这些变化似乎是活动期间钙离子进入细胞的结果，因为钙离子在细胞外空间的扩散特性并无异常。[Ca2+]0的降低会降低神经元兴奋性的阈值，但会减少突触传递；对这些效应进行了粗略的数值估计。在某些情况下，这些效应足够大，足以表明但不能证明[Ca2+]0的变化可能具有调节作用。然而，[Ca2+]0的变化被视为神经系统中钙离子介导过程的一个有价值的指标。
