title: Fine structure of hippocampal mossy fiber synapses following rapid high-pressure freezing.
abstract: Synapses of hippocampal neurons play important roles in learning and memory processes and are involved in aberrant hippocampal function in temporal lobe epilepsy. Major neuronal types in the hippocampus as well as their input and output synapses are well known, but it has remained an open question to what extent conventional electron microscopy (EM) has provided us with the real appearance of synaptic fine structure under in vivo conditions. There is reason to assume that conventional aldehyde fixation and dehydration lead to protein denaturation and tissue shrinkage, likely associated with the occurrence of artifacts. However, realistic fine-structural data of synapses are required for our understanding of the transmission process and for its simulation. Here, we used high-pressure freezing and cryosubstitution of hippocampal tissue that was not subjected to aldehyde fixation and dehydration in ethanol to monitor the fine structure of an identified synapse in the hippocampal CA3 region, that is, the synapse between granule cell axons, the mossy fibers, and the proximal dendrites of CA3 pyramidal neurons. Our results showed that high-pressure freezing nicely preserved ultrastructural detail of this particular synapse and allowed us to study rapid structural changes associated with synaptic plasticity.
authors.affiliation: Department of Structural Neurobiology, Center for Molecular Neurobiology Hamburg , University of Hamburg, Martinistrasse 52, Hamburg, Germany.
authors.forename: Shanting
authors.initials: S
authors.lastname: Zhao
authors.forename: Daniel
authors.initials: D
authors.lastname: Studer
authors.forename: Werner
authors.initials: W
authors.lastname: Graber
authors.forename: Sigrun
authors.initials: S
authors.lastname: Nestel
authors.forename: Michael
authors.initials: M
authors.lastname: Frotscher
mesh_terms: D000447:Aldehydes; D000818:Animals; D016477:Artifacts; D001834:Body Water / Q000378:metabolism; D056654:CA3 Region, Hippocampal / Q000473:pathology; D003890:Desiccation; D004833:Epilepsy, Temporal Lobe / Q000473:pathology; D000431:Ethanol; D005615:Freezing; D007202:Indicators and Reagents; D017774:Long-Term Potentiation; D051379:Mice; D009412:Nerve Fibers / Q000473:pathology / Q000648:ultrastructure*; D010477:Perfusion; D011489:Protein Denaturation; D017661:Receptors, Presynaptic / Q000648:ultrastructure; D013569:Synapses / Q000473:pathology / Q000648:ultrastructure*; D009435:Synaptic Transmission / Q000502:physiology; D046509:Tissue Culture Techniques; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D000447:Aldehydes; D007202:Indicators and Reagents; D017661:Receptors, Presynaptic; D000431:Ethanol