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Structural Determinants of Transmission at Large Hippocampal Mossy Fiber Synapses

Biomedical Sciences Research Institute Computer Science Research Institute Environmental Sciences Research Institute Nanotechnology & Advanced Materials Research Institute

Rollenhagen, Astrid, Saetzler, Kurt, Rodriguez, Peter, Frotscher, Michael and Lübke, Joachim H. R. (2007) Structural Determinants of Transmission at Large Hippocampal Mossy Fiber Synapses. J. Neurosci., 27 (39). pp. 10434-10444. [Journal article]

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URL: http://www.jneurosci.org/cgi/content/abstract/27/39/10434

DOI: 10.1523/JNEUROSCI.1946-07.2007

Abstract

Synapses are the key elements for signal processing and plasticity in the brain. To determine the structural factors underlying the unique functional properties of the hippocampal mossy fiber synapse, the complete quantitative geometry was investigated, using electron microscopy of serial ultrathin sections followed by computer-assisted three-dimensional reconstruction. In particular, parameters relevant for transmitter release and synaptic plasticity were examined. Two membrane specializations were found: active zones (AZs), transmitter release sites, and puncta adherentia, putative adhesion complexes. Individual boutons had, on average, 25 AZs (range, 745) that varied in shape and size (mean, 0.1 microm2; range, 0.070.17 microm2). The mean distance between individual AZs was 0.45 microm. Mossy fiber boutons and their target structures were mostly ensheathed by astrocytes, but fine glial processes never reached the active zones. Two structural factors are likely to promote synaptic cross talk: the short distance between AZs and the absence of fine glial processes at AZs. Thus, synaptic cross talk may contribute to the efficacy of hippocampal mossy fiber synapses. On average, a bouton contained 20,400 synaptic vesicles; [~]900 vesicles were located within 60 nm from the active zone, [~]4400 between 60 and 200 nm, and the remaining beyond 200 nm, suggesting large readily releasable, recycling, and reserve pools. The organization of the different pools may be a key structural correlate of presynaptic plasticity at this synapse. Thus, the mossy fiber bouton differs fundamentally in structure and function from the calyx of Held and other central synapses.

Item Type:Journal article
Faculties and Schools:Faculty of Life and Health Sciences
Faculty of Life and Health Sciences > School of Biomedical Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Molecular Medicine
Biomedical Sciences Research Institute > Molecular Medicine > Neuroscience & Neurodegenerative Diseases
ID Code:3776
Deposited By:Dr Kurt Saetzler
Deposited On:01 Feb 2010 10:21
Last Modified:10 Jun 2010 10:49

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