Mironov S L, Lux H D
Department of Neurophysiology, Max-Planck-Institute for Psychiatry, Planegg-Martinsried, Germany.
Pflugers Arch. 1993 Jul;424(2):183-91. doi: 10.1007/BF00374610.
Digital imaging of fura-2 fluorescence and the voltage-clamp technique were combined to study cytoplasmic free Ca2+ concentration, [Ca]i, in neurons cultured from chick dorsal root ganglia. Depolarizing pulses raised [Ca]i to a new steady-state level which was achieved earlier in neurites than in the soma. The rise in [Ca]i during stimulated bursting or rhythmic activity was also faster in neurites. After stimulation [Ca]i recovered monoexponentially in the soma and biexponentially in neurites. Application of 50 mM KCl produced membrane depolarization and a concomitant increase of [Ca]i. During wash-out [Ca]i often declined to an intermediate steady-state level at which it stayed for several minutes. Thereafter the resting level of [Ca]i was quickly restored. [Ca]i recovery was delayed after treating the cell with 2 microM thapsigargin, an inhibitor of the Ca2+ pump of internal Ca2+ stores. Caffeine (10 mM) transiently increased [Ca]i. A second caffeine application produced smaller [Ca]i changes due to the prior depletion of Ca2+ stores, which could be replenished by brief exposure to KCl. Thapsigargin (2 microM) transiently increased [Ca]i both in the standard and Ca(2+)-free solution. [Ca]i transients due to caffeine and thapsigargin started in the cell interior, in contrast to [Ca]i changes evoked by membrane depolarization, which were noticed first at the cell edge. Caffeine and thapsigargin induced a transient inward current which persisted in the presence of 1 mM La3+ and in Ca(2+)-free solutions, but which was greatly diminished in Na(+)-free solutions. The effects of caffeine and thapsigargin were mutually exclusive both in the generation of [Ca]i transients and in the inward current induction.
将fura - 2荧光的数字成像与电压钳技术相结合，研究从鸡背根神经节培养的神经元中的细胞质游离Ca2 +浓度[Ca]i。去极化脉冲将[Ca]i提高到一个新的稳态水平，神经突比胞体更早达到该水平。在刺激爆发或节律性活动期间，神经突中[Ca]i的升高也更快。刺激后，胞体中的[Ca]i以单指数形式恢复，神经突中则以双指数形式恢复。施加50 mM KCl会导致膜去极化，并伴随[Ca]i的增加。在洗脱过程中，[Ca]i常常下降到一个中间稳态水平，并在该水平维持几分钟。此后，[Ca]i的静息水平迅速恢复。用2 microM毒胡萝卜素（一种内质网Ca2 +泵的抑制剂）处理细胞后，[Ca]i的恢复延迟。咖啡因（10 mM）使[Ca]i短暂增加。由于先前Ca2 +储存的耗尽，再次施加咖啡因引起的[Ca]i变化较小，短暂暴露于KCl可补充Ca2 +储存。毒胡萝卜素（2 microM）在标准溶液和无Ca(2 +)溶液中均使[Ca]i短暂增加。与膜去极化引起的[Ca]i变化（首先在细胞边缘被注意到）相反，咖啡因和毒胡萝卜素引起的[Ca]i瞬变始于细胞内部。咖啡因和毒胡萝卜素诱导了一个短暂的内向电流，该电流在1 mM La3 +存在下和无Ca(2 +)溶液中持续存在，但在无Na(+)溶液中大大减弱。咖啡因和毒胡萝卜素的作用在[Ca]i瞬变的产生和内向电流诱导方面都是相互排斥的。
