title: Ultrastructural analysis of adult mouse neocortex comparing aldehyde perfusion with cryo fixation.
abstract: Analysis of brain ultrastructure using electron microscopy typically relies on chemical fixation. However, this is known to cause significant tissue distortion including a reduction in the extracellular space. Cryo fixation is thought to give a truer representation of biological structures, and here we use rapid, high-pressure freezing on adult mouse neocortex to quantify the extent to which these two fixation methods differ in terms of their preservation of the different cellular compartments, and the arrangement of membranes at the synapse and around blood vessels. As well as preserving a physiological extracellular space, cryo fixation reveals larger numbers of docked synaptic vesicles, a smaller glial volume, and a less intimate glial coverage of synapses and blood vessels compared to chemical fixation. The ultrastructure of mouse neocortex therefore differs significantly comparing cryo and chemical fixation conditions.
authors.affiliation: BioEM Facility, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Natalya
authors.initials: N
authors.lastname: Korogod
authors.affiliation: Laboratory of Sensory Processing, Brain Mind Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Carl C H
authors.identifier: http://orcid.org/0000-0003-3344-4495
authors.initials: CC
authors.lastname: Petersen
authors.affiliation: BioEM Facility, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Graham W
authors.initials: GW
authors.lastname: Knott
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D005404:Fixatives / Q000378:metabolism; D005615:Freezing; D051379:Mice; D008854:Microscopy, Electron / Q000379:methods; D019579:Neocortex / Q000648:ultrastructure*; D010477:Perfusion; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D000447:Aldehydes; D005404:Fixatives
keywords: astrocyte; axon; dendrite; mouse; neuroscience; synapse; ultrastructure