Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 104, Issue 5, Pages 1697-1702Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0610741104
Keywords
cerebellum; mossy fibers; squid; synaptic vesicles
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Funding
- NINDS NIH HHS [NS13742, P01 NS013742] Funding Source: Medline
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Transmitter release at chemical synapses is triggered by high calcium concentration microprofiles at the presynaptic cytosol. Such microprofiles, generated by the opening of voltage-dependent calcium channels at the presynaptic plasma membrane, have been defined as calcium concentration microdomains. Using total internal reflection fluorescent microscopy in conjunction with calcium and vesicular release indicator dyes, we have directly visualized the close apposition of calcium concentration microdomains and synaptic release sites at single synaptic terminals from the CNS from rat cerebellar mossy fiber and squid optic lobe. These findings demonstrate the close apposition of calcium entry and release sites and the dynamics of such site locations over time. Kinetic analysis shows that vesicles can be released via two distinct mechanisms: full-fusion and kiss-and-run. Calcium triggers vesicular motion toward the membrane, and the speed of such movement is calcium concentration-dependent. Moreover, the immediately available vesicular pool represents molecularly trapped vesicles that can be located at a larger distance from the plasma membrane than the field illuminated by total internal reflection fluorescent microscopy.
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