Richards C D, Metcalfe J C, Smith G A, Hesketh T R
Biochim Biophys Acta. 1984 Apr 16;803(4):215-20. doi: 10.1016/0167-4889(84)90110-1.
The free cytoplasmic Ca2+ concentration [( Ca2+]i) in rat brain synaptosomes estimated by the indicator quin 2 is 104 +/- 8 nM (S.D.) in artificial cerebrospinal fluid (1.2 mM Ca2+), but decreases at lower Ca2+ concentrations in the medium. The presence of quin 2 in the synaptosomes does not affect either the spontaneous release of transmitter (gamma-aminobutyric acid) or the release induced by K+ depolarisation. In quin 2-loaded synaptosomes, depolarisation by K+ causes an abrupt increase in [Ca]i (less than 2-fold) that is approximately proportional to the extent of depolarisation, whereas depolarisation by veratrine alkaloids produces a slow rise in [Ca]i. The increase in [Ca]i produced by K+ depolarisation does not occur in the absence of Ca2+ in the medium. The data are consistent with a direct correlation between [Cai] and transmitter release in functional synaptosomes. The pH in synaptosomes estimated by the indicator quene 1 is 7.04 +/- 0.07 and is stable in media containing 5 mM bicarbonate. The pH in synaptosomes was decreased by protoveratrine but not by K+ depolarisation.
用喹啉2作为指示剂估算，大鼠脑突触体中的游离细胞质钙离子浓度[Ca2+]i在人工脑脊液（1.2 mM Ca2+）中为104±8 nM（标准差），但在培养基中钙离子浓度较低时会降低。突触体中喹啉2的存在既不影响递质（γ-氨基丁酸）的自发释放，也不影响由钾离子去极化诱导的释放。在加载了喹啉2的突触体中，钾离子去极化会导致[Ca]i突然增加（小于2倍），且增加幅度大致与去极化程度成正比，而藜芦碱生物碱去极化则会使[Ca]i缓慢上升。在培养基中不存在钙离子的情况下，钾离子去极化不会导致[Ca]i增加。这些数据与功能性突触体中[Ca]i与递质释放之间的直接相关性相符。用喹啉1作为指示剂估算，突触体中的pH值为7.04±0.07，在含有5 mM碳酸氢盐的培养基中保持稳定。突触体中的pH值会因原藜芦碱而降低，但不会因钾离子去极化而降低。
