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Structural plasticity of spines at giant mossy fiber synapses

Zhao, Shanting, Studer, Daniel, Chai, Xuejun, Graber, Werner, Brose, Nils, Nestel, Sigrun, Young, Christina, Rodriguez, E. Patricia, Saetzler, Kurt and Frotscher, Michael (2012) Structural plasticity of spines at giant mossy fiber synapses. Frontiers in Neural Circuits, 6 . [Journal article]

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DOI: 10.3389/fncir.2012.00103

Abstract

The granule cells of the dentate gyrus give rise to thin unmyelinated axons, the mossyfibers. They form giant presynaptic boutons impinging on large complex spines onthe proximal dendritic portions of hilar mossy cells and CA3 pyramidal neurons. Whilethese anatomical characteristics have been known for some time, it remained unclearwhether functional changes at mossy fiber synapses such as long-term potentiation(LTP) are associated with structural changes. Since subtle structural changes mayescape a fine-structural analysis when the tissue is fixed by using aldehydes and isdehydrated in ethanol, rapid high-pressure freezing (HPF) of the tissue was applied.Slice cultures of hippocampus were prepared and incubated in vitro for 2 weeks. Then,chemical LTP (cLTP) was induced by the application of 25mM tetraethylammonium (TEA)for 10min. Whole-cell patch-clamp recordings from CA3 pyramidal neurons revealeda highly significant potentiation of mossy fiber synapses when compared to controlconditions before the application of TEA. Next, the slice cultures were subjected to HPF,cryosubstitution, and embedding in Epon for a fine-structural analysis. When comparedto control tissue, we noticed a significant decrease of synaptic vesicles in mossy fiberboutons and a concomitant increase in the length of the presynaptic membrane. On thepostsynaptic side, we observed the formation of small, finger-like protrusions, emanatingfrom the large complex spines. These short protrusions gave rise to active zones that wereshorter than those normally found on the thorny excrescences. However, the total numberof active zones was significantly increased. Of note, none of these cLTP-induced structuralchanges was observed in slice cultures from Munc13-1 deficient mouse mutants showingseverely impaired vesicle priming and docking. In conclusion, application of HPF allowedus to monitor cLTP-induced structural reorganization of mossy fiber synapses.

Item Type:Journal article
Keywords:synaptic ultrastructure, high-pressure freezing, mossy fiber LTP, dendritic spine, actin cytoskeleton, dentate gyrus, granule cells, 3D reconstrucion
Faculties and Schools:Faculty of Life and Health Sciences > School of Biomedical Sciences
Faculty of Life and Health Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Genomic Medicine
Biomedical Sciences Research Institute > Nutrition Innovation Centre for Food and Health (NICHE)
ID Code:24318
Deposited By: Dr Kurt Saetzler
Deposited On:23 Feb 2016 09:49
Last Modified:23 May 2017 15:54

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