Lines in the XY plane. Blue dashed lines, active zone borders; brown dots, VGCCs; black dots, space occupied by vesicles; gray circles, vesicle projections on the XY plane; green dots, locationsNat Neurosci. Author manuscript; obtainable in PMC 2014 September 27.Ermolyuk et al.Pageof Ca2+-release sensors, grid five nm. (d) Simulation outcomes corresponding to geometries in (c). Best, action possible waveform; middle, typical [Ca2+] transients at Ca2+-release sensors; bottom, corresponding release rates; legends, resulting fusion probabilities pv. (e) Cumulative probability plots of pv for Clustered and Random models. (n = 28 vesicles from 7 simulated synapses for each model). (f) Cumulative probability plots displaying the typical variety of VGCCs located inside a provided distance from the vesicular Ca2+-release sensors (n = 240 vesicles from 60 simulated synapses). (g) Model predictions for inhibition of evoked release by BAPTA and EGTA. Dotted lines show the experimental effects of BAPTA-AM and EGTA-AM as determined in Fig. 4e. (h) Dependency of pv on [Ca2+]total simulated by progressive deletion of active VGCCs. Data are from five simulated synapses, each point represents average pv for 4 release-ready vesicles. Data on each axes are normalized towards the corresponding maximal values at basal circumstances. Dotted lines, fitted energy function, with all the slope corresponding to Ca2+ present cooperativity mICa = 2.46.Europe PMC Funders Author Manuscripts Europe PMC Funders Author ManuscriptsNat Neurosci. Author manuscript; offered in PMC 2014 September 27.Ermolyuk et al.PageEurope PMC Funders Author Manuscripts Europe PMC Funders Author ManuscriptsFigure 7.Modeling VGCC-dependent glutamate miniature release. (a) Schematics illustrating VCell simulations. As in Fig. 6c the black dot indicate space taken up by the vesicle inside the XY plane 2.five nm above the active zone; gray circle, vesicle projection around the active zone plane; green dots, assumed positions of Ca2+-release sensors, grid five nm. (b) Examples of average [Ca2+] transients at release sensors made by single VGCC openings (for 0.33 ms) for 4 unique VGCC-release sensor distances. Insert, corresponding vesicle fusion probabilities. (c) Color-coded map displaying dependency of vesicle fusion probability pv(t,d) on VGCC-Nat Neurosci. Author manuscript; readily available in PMC 2014 September 27.Ermolyuk et al.Pagevesicle distance d and VGCC open-channel duration t. (d) Frequency histograms (t) for the durations of spontaneous P/Q-, N-, and R-type channel opening at Vrest obtained employing the VGCC gating model12 (Fig.1445951-89-2 Chemscene 5a).1377584-27-4 manufacturer (e) Dependencies of vesicle fusion probability pv(d) on VGCC-vesicle distance for unique VGCC subtypes.PMID:27108903 (f) Frequency histogram (d) for the relative VGCC-vesicle distances within the Clustered model (n = 60 simulated active zones). (g) Dependency of spontaneous P/Q-, N-, and R-type channel opening on Vrest, calculated using the six-state VGCC gating model12 (Fig. 5a). (h) Distribution of Vrest in cultured hippocampal neurons (mean 71.9 ?0.7 mV, n = 98 neurons). (i) Cumulative fractions of VGCC-mediated mEPSCs and VGCC numbers plotted as functions of the distance from the vesicular release sensor. 90 of all VGCC-dependent minis are mediated by only 20 of all VGCCs present within the active zone situated inside 70 nm of docked vesicles. (j) Model predictions for the effects of BAPTA and EGTA on VGCC-dependent mEPSC frequency. Dotted lines, experimental effects of BAPTA-AM and EGTA-AM as estimated i.
