New ways of looking at synapses |
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Authors: | Michael Frotscher Shanting Zhao Werner Graber Alexander Drakew Daniel Studer |
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Institution: | (1) Institute of Anatomy and Cell Biology, University of Freiburg, Albertstr. 17, 79104 Freiburg, Germany;(2) Institute of Anatomy, University of Bern, Balzerstr. 2, 3000 Bern 9, Switzerland |
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Abstract: | Current concepts of synaptic fine-structure are derived from electron microscopic studies of tissue fixed by chemical fixation
using aldehydes. However, chemical fixation with glutaraldehyde and paraformaldehyde and subsequent dehydration in ethanol
result in uncontrolled tissue shrinkage. While electron microscopy allows for the unequivocal identification of synaptic contacts,
it cannot be used for real-time analysis of structural changes at synapses. For the latter purpose advanced fluorescence microscopy
techniques are to be applied which, however, do not allow for the identification of synaptic contacts. Here, two approaches
are described that may overcome, at least in part, some of these drawbacks in the study of synapses. By focusing on a characteristic,
easily identifiable synapse, the mossy fiber synapse in the hippocampus, we first describe high-pressure freezing of fresh
tissue as a method that may be applied to study subtle changes in synaptic ultrastructure associated with functional synaptic
plasticity. Next, we propose to label presynaptic mossy fiber terminals and postsynaptic complex spines on CA3 pyramidal neurons
by different fluorescent dyes to allow for the real-time monitoring of these synapses in living tissue over extended periods
of time. We expect these approaches to lead to new insights into the structure and function of central synapses.
Robert Feulgen Lecture presented at the 49th Symposium of the Society for Histochemistry in Freiburg i.Br., Germany, 26-29
September 2007. |
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Keywords: | Synapse structure High-pressure freezing Real-time microscopy Mossy fiber Dendritic spines |
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