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Cell Rep. 2020 Mar 17;30(11):3632-3643.e8. doi: 10.1016/j.celrep.2020.02.083.

Ultrastructural Correlates of Presynaptic Functional Heterogeneity in Hippocampal Synapses.

Author information

1
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Georg August University, School of Science, 37073 Göttingen, Germany.
2
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany.
3
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
4
Institute for Neuro- and Sensory Physiology, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany.
5
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany. Electronic address: imig@em.mpg.de.
6
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany. Electronic address: cooper@em.mpg.de.

Abstract

Although similar in molecular composition, synapses can exhibit strikingly distinct functional transmitter release and plasticity characteristics. To determine whether ultrastructural differences co-define this functional heterogeneity, we combine hippocampal organotypic slice cultures, high-pressure freezing, freeze substitution, and 3D-electron tomography to compare two functionally distinct synapses: hippocampal Schaffer collateral and mossy fiber synapses. We find that mossy fiber synapses, which exhibit a lower release probability and stronger short-term facilitation than Schaffer collateral synapses, harbor lower numbers of docked synaptic vesicles at active zones and a second pool of possibly tethered vesicles in their vicinity. Our data indicate that differences in the ratio of docked versus tethered vesicles at active zones contribute to distinct functional characteristics of synapses.

KEYWORDS:

active zone; electron microscopy; hippocampal mossy fiber synapse; release probability; short-term plasticity; synapse; synaptic vesicles; ultrastructure; vesicle docking; vesicle priming

PMID:
32187536
DOI:
10.1016/j.celrep.2020.02.083
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Conflict of interest statement

Declaration of Interests The authors declare no competing interests.

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