This title appears in the Scientific Report :
2017
Please use the identifier:
http://hdl.handle.net/2128/15052 in citations.
Synaptic organization in layer 5 of the human temporal lobe: A quantitative electron microscopic analysis
Synaptic organization in layer 5 of the human temporal lobe: A quantitative electron microscopic analysis
Synapses are the key elements for signal transduction and plasticity in the brain, thus controlling the induction, maintenance and termination of signal transduction in any given neuronal microcircuit.Despite a relatively large number of publications on structural and functional aspects of various s...
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Personal Name(s): | Yakoubi, Rachida (First author) |
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Rollenhagen, Astrid / Marec, von Lehe / Kurt, Sätzler / Lübke, Joachim (Corresponding author) | |
Contributing Institute: |
Molekulare Organisation des Gehirns; INM-2 JARA-BRAIN; JARA-BRAIN |
Imprint: |
2016
|
Conference: | SfN's 46th annual meeting, San Diego (USA), 2016-11-12 - 2016-11-16 |
Document Type: |
Poster |
Research Program: |
Connectivity and Activity |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
Synapses are the key elements for signal transduction and plasticity in the brain, thus controlling the induction, maintenance and termination of signal transduction in any given neuronal microcircuit.Despite a relatively large number of publications on structural and functional aspects of various synapses in the central nervous system of different animal species, very little is known about these structures in humans, in particular about their quantitative geometry. Hence, synapses in cortical layer 5 - the main output station of the neocortex and a recipient layer of thalamocortical afferents of the human temporal lobe - were investigated using serial ultrathin sectioning and digital electron microscopic images. This was followed by three dimensional (3D) volume reconstructions leading in the generation of quantitative 3D-models of synapses. We focused on structural parameters that are the most critical factors underlying synaptic transmission and plasticity, such as the shape, size, number, and distribution of active zones (AZs, functional transmitter release sites) as well as the organization and size of the three pools of synaptic vesicles, namely the readily releasable, the recycling and reserve pool. In addition, immunohistochemistry against glutamine synthetase was carried out to investigate the structural relationship of synapses and astrocytes and thus their contribution to synaptic transmission and plasticity.A total of 152 synaptic boutons and their target structures were completely analyzed. The majority were established either on dendritic spines (~76%) the remainder on shafts. Synaptic boutons were highly variable in both shape and size (6.20±0.77 μm2; 0.42±0.07 μm3, ranging from 0.46 to 27.33 μm2; 0.10 to 1.93 μm3) with a skew to middle-sized boutons. Several mitochondria (0-26) were found in the presynaptic bouton constituting ~6% of the total volume. The majority of boutons (~88%) had a single pre- (0.452±0.358 µm2; 0.003±0,001 μm3) and postsynaptic densities (0.405±0.100 μm2; 0.01±0.01 μm3), sometimes perforated. The mean total pool size of synaptic vesicles was 1580.19±255.19 (ranging from 142 to 8413) with a mean diameter of 31.99±0.87 nm. Strikingly, no correlation was found between the size of the boutons with that of mitochondria, AZs and the pool of vesicles. Synaptic complexes were surrounded by a dense network of fine astrocytic processes reaching the synaptic cleft, thus regulating the temporal and spatial glutamate concentration.The quantitative 3D-models of synapses will lead to an improved understanding of the function of synapses in cortical networks in humans. |