Nicholson C, Bruggencate G T, Steinberg R, Stöckle H
Proc Natl Acad Sci U S A. 1977 Mar;74(3):1287-90. doi: 10.1073/pnas.74.3.1287.
Changes in extracellular Ca2+ concentration were directly measured in the rat cerebellum, using an ion-selective micropipette. Extracellular K+ was measured simultaneously with a second ion-selective micropipette. The potential reference barrels of the ion electrodes also provided fast field and slow potentials. During repetitive stimulation of the parallel fiber--Purkinje cell cerebellar circuit, extracellular Ca2+ fell to about 80% of base line concentration. During the spreading depression of Leão, extracellular Ca2+ fell to about 10% of base line; decreases of this magnitude also occurred during terminal anoxia. In all cases extracellular K+ increased substantially. These results show that extracellular Ca2+ is modulated during neuronal activity in the central nervous system and that under some conditions the Ca2+ change can be extreme. Given the well-established and antagonistic effects of reduce extracellular Ca2+ on axonal excitability and synaptic transmission, these results suggest that Ca2+ modulation in the brain cell microenvironment may be a significant parameter in the behavior of neuronal ensembles.
使用离子选择性微电极直接测量大鼠小脑中细胞外Ca2+浓度的变化。同时用第二个离子选择性微电极测量细胞外K+。离子电极的电位参考管还提供快速场电位和慢电位。在平行纤维-浦肯野细胞小脑回路的重复刺激过程中，细胞外Ca2+降至基线浓度的约80%。在Leão的扩散性抑制期间，细胞外Ca2+降至基线的约10%；在末期缺氧期间也出现了这种程度的下降。在所有情况下，细胞外K+都大幅增加。这些结果表明，在中枢神经系统的神经元活动期间，细胞外Ca2+受到调节，并且在某些情况下，Ca2+的变化可能非常剧烈。鉴于降低细胞外Ca²⁺对轴突兴奋性和突触传递具有既定的拮抗作用，这些结果表明，脑细胞微环境中的Ca²⁺调节可能是神经元群体行为的一个重要参数。
