Article Figures & Data
Figures
- Figure 1.
VGCC-mediated Ca2+ influx regulates spontaneous vesicle release. A, Sampled presynaptic recording. Top, Depolarization at 20 ms from −80 to 0 mV; middle, Ca2+ current trace; bottom two panels, current traces (red) recorded after 1 and 2 min extracellular application of 0.2 mm Cd2+ contained bath solution. B, Normalized electrical charge of Ca2+ influx versus time (n = 5). C, Sampled mini traces before and after switching to normal (Ctrl, n = 17) and Cd2+ contained 2 mm [Ca2+]e bath solution (Cd2+, n = 8, red). D, Average of normalized plot of mini frequency versus time at 2 mm [Ca2+]e. E, Sampled mini traces before and after switching to normal (Ctrl, n = 11), and Cd2+ contained 8 mm [Ca2+]e bath solution (Cd2+, n = 8, red). F, Average of normalized plot of mini frequency versus time at 8 mm [Ca2+]e. All the data in D and F were normalized to the recordings at the time of solution switching (as indicated by the arrowhead). G, H, Cumulative probability of mEPSC amplitude before (black solid) and after (red dash) switching to normal (left) or Cd2+ (right) contained bath solution, with [Ca2+]e of 2 mm (G) and [Ca2+]e of 8 mm (H), respectively. Error bars indicate ±SEM. *p < 0.05.
- Figure 2.
Ca2+ current and its temporal correlation with spontaneous minis. A, Single calcium channel currents obtained by cell-attached patch recording at the release face, with the different [Ca2+]pipette (holding potential of 0 mV). B, Statistics of single Ca2+ channel current amplitude versus [Ca2+]pipette. C, Left, Sampled presynaptic (at resting potential, −66 mV) and postsynaptic current recording (holding potential of −80 mV) at [Ca2+]e of 2 mm. Right, The scaled single mini contained paired currents at the asterisk in the left. D, Left, The averaged presynaptic current aligned at the onset (differential peak) of the minis (51,730 events); the inset shows the paired currents before the onset of the mini event. The presynaptic current was low-pass filtered at 5 kHz. E, Same plot as in C but with [Ca2+]e of 8 mm. F, Same plot as in D but with [Ca2+]e of 8 mm and 25,261 events averaging. G, Top, Sample of a recorded presynaptic current trace. Bottom, Sample of a simulated trace with pseudo white noise; the current traces in the boxes of the left panels were displayed with greater details in the right panels. H, The distribution of noise level of the recorded presynaptic currents (black solid) and the simulated pseudo white noise traces (red dash). I, Histogram of opening lifetime of 751 single VGCC open events by cell-attached recording. J, The cumulative probability distribution of single VGCCs opening lifetime. K, L, Top, Simulated uniform distribution (K) or Gaussian distribution (L) of single-channel opening time points (20,000 events for each distribution). Bottom, The simulated traces as average of 50,000 pseudo white noise traces including embedded 20,000 single-channel open events with corresponding distributions. Error bars indicate ±SEM.
- Figure 3.
Ca2+ current and its temporal correlation with capacitance up-step in cell-attached recording at presynaptic release site. A, Sampled presynaptic imaginary (Im) and real (Re) part of lock-in signals, as well as ICa trace by cell-attached patch recording at the release face. The inward unitary current indicates single VGCC activity. B, Sampled presynaptic imaginary (Im) and real (Re) part of lock-in signals, as well as ICa trace by cell-attached patch recording at the release face. The up-step of Im corresponds to a single vesicle fusion event-related membrane capacitance change. C, The averaged Im, Re, and ICa traces aligned by the onset of capacitance from 52 spontaneous events. The timescale calibration is applicable to all the plots.
- Figure 4.
[Ca2+]e dependence of mini frequency in WT and Syt-2 KO synapses. A, Sampled mini traces recorded at different [Ca2+]e in WT and KO synapses. B, [Ca2+]e dependence of mini frequency obtained from WT (black) and KO (red) synapses. Data were scaled in logarithm coordinates and linearly regressed with a cooperativity of 0.43 for WT (black) and 0.47 for KO (red). Error bars indicate ±SEM.
