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Nanoscale distribution of presynaptic Ca(2+) channels and its impact on vesicular release during development.

Nakamura Y, Harada H, Kamasawa N, Matsui K, Rothman JS, Shigemoto R, Silver RA, DiGregorio DA, Takahashi T - Neuron (2014)

Bottom Line: Between postnatal day 7 and 21, VGCCs formed variable sized clusters and vesicular release became less sensitive to EGTA, whereas fixed Ca(2+) buffer properties remained constant.Experimentally constrained reaction-diffusion simulations suggest that Ca(2+) sensors for vesicular release are located at the perimeter of VGCC clusters (<30 nm) and predict that VGCC number per cluster determines vesicular release probability without altering release time course.This "perimeter release model" provides a unifying framework accounting for developmental changes in both synaptic efficacy and time course.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Synaptic Function, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan; Cellular & Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, Okinawa 904-0495, Japan; Laboratory of Dynamic Neuronal Imaging, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France; CNRS UMR 3571, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.

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Developmental Changes in Vesicular Release Time Course Are Predicted by Perimeter Release Model(A) Representative examples of experimentally measured presynaptic APs, EPSCs, and vesicular release rates before (black) and after (gray) presynaptic perfusion of 10 mM EGTA in P7 and P14 calyces. Dashed lines indicate peak scaked release rate in 10 mM EGTA.(B) Mean synaptic delay (from the 50% rise time of the APs to the 20% rise time of the EPSCs, ± SEM) in the presence of 0.1 mM (open bars) or 10 mM EGTA (filled bars) in the presynaptic pipette solution (n = 10 calyces for P7, n = 8 for P14 and P21).(C) Release half duration (the width at half maximal of the release rate, ± SEM) in the presence of 0.1 mM and 10 mM EGTA, estimated by deconvolution at P7, P14, and P21 (∗∗p < 0.01, one-way ANOVA). Internal perfusion of 10 mM EGTA reduced the release duration by ∼15% in P14 and P21 (∗∗p < 0.05, paired t test), but not in P7 calyces.(D) Dependence of release duration on the PCD for AP7 (green) and AP14 (black) waveforms, simulated with the perimeter release model. Red circles indicate values predicted by experimental results, and an arrow indicates the direction of developmental change.(E) Same as (D) but for synaptic delay.(F) Temporally aligned simulated traces of the [Ca2+] and vesicular release rate for [EGTA] = 0.1 mM (black) and 10 mM (gray). For P7 and P14 simulations, the timing and duration of Ca2+ entry, number of open VGCCs, Ca2+ sensor affinity, and PCD for were adjusted specifically for each age.(G) The simulated effect of 10 mM EGTA on synaptic delay and vesicular release duration for the perimeter release model.(H) Cartoons showing possible AZ topographies for VGCCs and synaptic vesicles released by a single AP. Model 1, random placement of vesicles and VGCCs within AZ. Model 2, vesicles surrounded by rings of VGCCs. Model 3, random placement of vesicles and VGCC clusters, including within vesicle clusters. Model 4, perimeter release model, where releasable synaptic vesicles are positioned at the perimeter of a VGCC cluster. Whether there are more than one releasable vesicle is only speculative.
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fig8: Developmental Changes in Vesicular Release Time Course Are Predicted by Perimeter Release Model(A) Representative examples of experimentally measured presynaptic APs, EPSCs, and vesicular release rates before (black) and after (gray) presynaptic perfusion of 10 mM EGTA in P7 and P14 calyces. Dashed lines indicate peak scaked release rate in 10 mM EGTA.(B) Mean synaptic delay (from the 50% rise time of the APs to the 20% rise time of the EPSCs, ± SEM) in the presence of 0.1 mM (open bars) or 10 mM EGTA (filled bars) in the presynaptic pipette solution (n = 10 calyces for P7, n = 8 for P14 and P21).(C) Release half duration (the width at half maximal of the release rate, ± SEM) in the presence of 0.1 mM and 10 mM EGTA, estimated by deconvolution at P7, P14, and P21 (∗∗p < 0.01, one-way ANOVA). Internal perfusion of 10 mM EGTA reduced the release duration by ∼15% in P14 and P21 (∗∗p < 0.05, paired t test), but not in P7 calyces.(D) Dependence of release duration on the PCD for AP7 (green) and AP14 (black) waveforms, simulated with the perimeter release model. Red circles indicate values predicted by experimental results, and an arrow indicates the direction of developmental change.(E) Same as (D) but for synaptic delay.(F) Temporally aligned simulated traces of the [Ca2+] and vesicular release rate for [EGTA] = 0.1 mM (black) and 10 mM (gray). For P7 and P14 simulations, the timing and duration of Ca2+ entry, number of open VGCCs, Ca2+ sensor affinity, and PCD for were adjusted specifically for each age.(G) The simulated effect of 10 mM EGTA on synaptic delay and vesicular release duration for the perimeter release model.(H) Cartoons showing possible AZ topographies for VGCCs and synaptic vesicles released by a single AP. Model 1, random placement of vesicles and VGCCs within AZ. Model 2, vesicles surrounded by rings of VGCCs. Model 3, random placement of vesicles and VGCC clusters, including within vesicle clusters. Model 4, perimeter release model, where releasable synaptic vesicles are positioned at the perimeter of a VGCC cluster. Whether there are more than one releasable vesicle is only speculative.

Mentions: During the period of hearing acquisition, the synaptic delay between the presynaptic AP and the EPSC becomes shorter, and the time course of vesicular release becomes faster at the calyx of Held (Taschenberger and von Gersdorff, 2000; Taschenberger et al., 2005). Numerical simulations suggest that these developmental changes might be mediated by alterations in the VGCC-sensor distance (Bucurenciu et al., 2008), but other findings argue against this hypothesis (Meinrenken et al., 2002). We re-examined this issue by measuring the synaptic delay and time course of vesicular release during EGTA dialysis. Our results show that internal perfusion of 10 mM EGTA had no effect on the synaptic delay at any age investigated, whereas the synaptic delay became shorter between P7 to P21 (Figures 8A and 8B). Moreover, internal perfusion of 10 mM EGTA produced only a modest reduction in the time course of vesicular release at P14 and P21 (∼10%), and no change at P7, whereas the half duration of release was reduced by 29% from P7 to P14 (Figure 8C), as previously reported (Taschenberger et al., 2005).


Nanoscale distribution of presynaptic Ca(2+) channels and its impact on vesicular release during development.

Nakamura Y, Harada H, Kamasawa N, Matsui K, Rothman JS, Shigemoto R, Silver RA, DiGregorio DA, Takahashi T - Neuron (2014)

Developmental Changes in Vesicular Release Time Course Are Predicted by Perimeter Release Model(A) Representative examples of experimentally measured presynaptic APs, EPSCs, and vesicular release rates before (black) and after (gray) presynaptic perfusion of 10 mM EGTA in P7 and P14 calyces. Dashed lines indicate peak scaked release rate in 10 mM EGTA.(B) Mean synaptic delay (from the 50% rise time of the APs to the 20% rise time of the EPSCs, ± SEM) in the presence of 0.1 mM (open bars) or 10 mM EGTA (filled bars) in the presynaptic pipette solution (n = 10 calyces for P7, n = 8 for P14 and P21).(C) Release half duration (the width at half maximal of the release rate, ± SEM) in the presence of 0.1 mM and 10 mM EGTA, estimated by deconvolution at P7, P14, and P21 (∗∗p < 0.01, one-way ANOVA). Internal perfusion of 10 mM EGTA reduced the release duration by ∼15% in P14 and P21 (∗∗p < 0.05, paired t test), but not in P7 calyces.(D) Dependence of release duration on the PCD for AP7 (green) and AP14 (black) waveforms, simulated with the perimeter release model. Red circles indicate values predicted by experimental results, and an arrow indicates the direction of developmental change.(E) Same as (D) but for synaptic delay.(F) Temporally aligned simulated traces of the [Ca2+] and vesicular release rate for [EGTA] = 0.1 mM (black) and 10 mM (gray). For P7 and P14 simulations, the timing and duration of Ca2+ entry, number of open VGCCs, Ca2+ sensor affinity, and PCD for were adjusted specifically for each age.(G) The simulated effect of 10 mM EGTA on synaptic delay and vesicular release duration for the perimeter release model.(H) Cartoons showing possible AZ topographies for VGCCs and synaptic vesicles released by a single AP. Model 1, random placement of vesicles and VGCCs within AZ. Model 2, vesicles surrounded by rings of VGCCs. Model 3, random placement of vesicles and VGCC clusters, including within vesicle clusters. Model 4, perimeter release model, where releasable synaptic vesicles are positioned at the perimeter of a VGCC cluster. Whether there are more than one releasable vesicle is only speculative.
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Related In: Results  -  Collection

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fig8: Developmental Changes in Vesicular Release Time Course Are Predicted by Perimeter Release Model(A) Representative examples of experimentally measured presynaptic APs, EPSCs, and vesicular release rates before (black) and after (gray) presynaptic perfusion of 10 mM EGTA in P7 and P14 calyces. Dashed lines indicate peak scaked release rate in 10 mM EGTA.(B) Mean synaptic delay (from the 50% rise time of the APs to the 20% rise time of the EPSCs, ± SEM) in the presence of 0.1 mM (open bars) or 10 mM EGTA (filled bars) in the presynaptic pipette solution (n = 10 calyces for P7, n = 8 for P14 and P21).(C) Release half duration (the width at half maximal of the release rate, ± SEM) in the presence of 0.1 mM and 10 mM EGTA, estimated by deconvolution at P7, P14, and P21 (∗∗p < 0.01, one-way ANOVA). Internal perfusion of 10 mM EGTA reduced the release duration by ∼15% in P14 and P21 (∗∗p < 0.05, paired t test), but not in P7 calyces.(D) Dependence of release duration on the PCD for AP7 (green) and AP14 (black) waveforms, simulated with the perimeter release model. Red circles indicate values predicted by experimental results, and an arrow indicates the direction of developmental change.(E) Same as (D) but for synaptic delay.(F) Temporally aligned simulated traces of the [Ca2+] and vesicular release rate for [EGTA] = 0.1 mM (black) and 10 mM (gray). For P7 and P14 simulations, the timing and duration of Ca2+ entry, number of open VGCCs, Ca2+ sensor affinity, and PCD for were adjusted specifically for each age.(G) The simulated effect of 10 mM EGTA on synaptic delay and vesicular release duration for the perimeter release model.(H) Cartoons showing possible AZ topographies for VGCCs and synaptic vesicles released by a single AP. Model 1, random placement of vesicles and VGCCs within AZ. Model 2, vesicles surrounded by rings of VGCCs. Model 3, random placement of vesicles and VGCC clusters, including within vesicle clusters. Model 4, perimeter release model, where releasable synaptic vesicles are positioned at the perimeter of a VGCC cluster. Whether there are more than one releasable vesicle is only speculative.
Mentions: During the period of hearing acquisition, the synaptic delay between the presynaptic AP and the EPSC becomes shorter, and the time course of vesicular release becomes faster at the calyx of Held (Taschenberger and von Gersdorff, 2000; Taschenberger et al., 2005). Numerical simulations suggest that these developmental changes might be mediated by alterations in the VGCC-sensor distance (Bucurenciu et al., 2008), but other findings argue against this hypothesis (Meinrenken et al., 2002). We re-examined this issue by measuring the synaptic delay and time course of vesicular release during EGTA dialysis. Our results show that internal perfusion of 10 mM EGTA had no effect on the synaptic delay at any age investigated, whereas the synaptic delay became shorter between P7 to P21 (Figures 8A and 8B). Moreover, internal perfusion of 10 mM EGTA produced only a modest reduction in the time course of vesicular release at P14 and P21 (∼10%), and no change at P7, whereas the half duration of release was reduced by 29% from P7 to P14 (Figure 8C), as previously reported (Taschenberger et al., 2005).

Bottom Line: Between postnatal day 7 and 21, VGCCs formed variable sized clusters and vesicular release became less sensitive to EGTA, whereas fixed Ca(2+) buffer properties remained constant.Experimentally constrained reaction-diffusion simulations suggest that Ca(2+) sensors for vesicular release are located at the perimeter of VGCC clusters (<30 nm) and predict that VGCC number per cluster determines vesicular release probability without altering release time course.This "perimeter release model" provides a unifying framework accounting for developmental changes in both synaptic efficacy and time course.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Synaptic Function, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan; Cellular & Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, Okinawa 904-0495, Japan; Laboratory of Dynamic Neuronal Imaging, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France; CNRS UMR 3571, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.

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Related in: MedlinePlus