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. 2004 May;86(5):2674–2690. doi: 10.1016/S0006-3495(04)74323-4

FIGURE 8.

FIGURE 8

The distribution of calcium in the whole terminal, as a function of time, during a train of seven impulses at a frequency of 50 Hz (Fig. 7 A) in the absence or presence of an endogenous buffer with the properties of BAPTA, according to the MC model and the facilitation molecular scheme; the ordinate gives the number of ions or molecules involved (cf. Fig. 3). (A) The number of free calcium ions. (B) The number of calcium ions bound to the mobile buffer. (C) The number of calcium ions bound to the fixed buffer. (D) The number of calcium ions bound to the pumps in the terminal walls. (E) The number of calcium ions pumped out through the terminal walls. (F) The number of calcium ions bound to the low-affinity sites for vesicles that have not yet undergone exocytosis. (G) The number of calcium ions bound to molecules in the high-affinity sites. (H) The number of calcium ions bound to BAPTA. Results are shown for three concentrations of BAPTA: 0 μM, 65 μM, and 196 μM; in panels A and B, the upper curve is for 0 μM, the middle curve for 65 μM, and the lower curve for 196 μM; in panels C–H, the solid line is for 0 μM, the dotted line for 65 μM, and the dashed line for 196 μM. For clarity, some of the data have been time averaged.