Morphometry of synaptic vesicles of the neuromuscular junction under different conditions of transmitter release

1988 ◽  
Vol 105 (3) ◽  
pp. 427-430
Author(s):  
O. M. Pozdnyakov ◽  
V. G. Nikulin
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Synaptic Vesicles

scholarly journals Transmitter release is evoked with low probability predominately by calcium flux through single channel openings at the frog neuromuscular junction

2015 ◽  
Vol 113 (7) ◽  
pp. 2480-2489 ◽  
Author(s):  
Fujun Luo ◽  
Markus Dittrich ◽  
Soyoun Cho ◽  
Joel R. Stiles ◽  
Stephen D. Meriney
Keyword(s):  
Neuromuscular Junction ◽  
Calcium Channels ◽  
Calcium Channel ◽  
Calcium Ions ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Vesicle Fusion ◽  
Frog Neuromuscular Junction ◽  
Low Probability ◽  
Presynaptic Calcium

The quantitative relationship between presynaptic calcium influx and transmitter release critically depends on the spatial coupling of presynaptic calcium channels to synaptic vesicles. When there is a close association between calcium channels and synaptic vesicles, the flux through a single open calcium channel may be sufficient to trigger transmitter release. With increasing spatial distance, however, a larger number of open calcium channels might be required to contribute sufficient calcium ions to trigger vesicle fusion. Here we used a combination of pharmacological calcium channel block, high-resolution calcium imaging, postsynaptic recording, and 3D Monte Carlo reaction-diffusion simulations in the adult frog neuromuscular junction, to show that release of individual synaptic vesicles is predominately triggered by calcium ions entering the nerve terminal through the nearest open calcium channel. Furthermore, calcium ion flux through this channel has a low probability of triggering synaptic vesicle fusion (∼6%), even when multiple channels open in a single active zone. These mechanisms work to control the rare triggering of vesicle fusion in the frog neuromuscular junction from each of the tens of thousands of individual release sites at this large model synapse.

Relative Distribution of Ca2+ Channels at the Crayfish Inhibitory Neuromuscular Junction

2004 ◽  
Vol 92 (3) ◽  
pp. 1491-1500 ◽  
Author(s):  
Tariq N. Allana ◽  
Jen-Wei Lin
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Single Channel ◽  
Procambarus Clarkii ◽  
Physiological Saline ◽  
Synaptic Delay ◽  
Similar Amount ◽  
Relative Distribution ◽  
P Type

We investigated the Ca2+ channel-synaptic vesicle topography at the inhibitor of the crayfish ( Procambarus Clarkii) neuromuscular junction (NMJ) by analyzing the effect of different modes of Ca2+ channel block on transmitter release. Initial identification of Ca2+ channels revealed the presence of two classes, P and non-P-type with P-type channels governing ∼70% of the total Ca2+ influx. The remaining Ca2+ influx was completely blocked by Cd2+ but not by saturating concentrations of ω-conotoxins MVIIC and GVIA, or nifedipine and SNX-482. To examine the relative spatial distribution of Ca2+ channels with respect to synaptic vesicles, we compared changes in inhibitory postsynaptic current amplitude and synaptic delay resulting from different spatial profiles of [Ca2+]i around release sites. Specifically, addition of either [Mg2+]o, which decreases single-channel current, or ω-Aga IVA, which completely blocks P-type channels, prolonged synaptic delay by a similar amount when Ca2+ influx block was <40%. Because non-P-type channels are able to compensate for blocked P-type channels, it suggests that these channels overlap considerably in their distribution. However, when Ca2+ influx was blocked by ∼50%, ω-Aga IVA increased delay significantly more than Mg2+, suggesting that P-type channels are located closer than non-P-type channels to synaptic vesicles. This distribution of Ca2+ channels was further supported by the observations that non-P-type channels are unable to trigger release in physiological saline and EGTA preferentially prolongs synaptic delay dominated by non-P-type channels when transmitter release is evoked with broad action potentials. We therefore conclude that although non-P-type channels do not directly trigger release under physiological conditions, their distribution partially overlaps with P-type channels.

Real-time measurement of transmitter release from single synaptic vesicles

Nature ◽  
1995 ◽  
Vol 377 (6544) ◽  
pp. 62-65 ◽  
Author(s):  
Dieter Bruns ◽  
Reinhard Jahn
Keyword(s):  
Real Time ◽  
Transmitter Release ◽  
Synaptic Vesicles ◽  
Time Measurement ◽  
Real Time Measurement

Influence of lanthanum on transmitter release at the neuromuscular junction

1971 ◽  
Vol 2 (3) ◽  
pp. 263-278 ◽  
Author(s):  
William A. DeBassio ◽  
Ronald M. Schnitzler ◽  
Rodney L. Parsons
Keyword(s):  
Neuromuscular Junction ◽  
Transmitter Release
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