Electron Tomography for the Study of Synaptic Ultrastructure in Fixed Brain Sections

Synaptic function depends upon interactions among sets of proteins that assemble into complex machines. Molecular biology, electrophysiology, and live-cell imaging studies have provided glimpses into the inner workings of the synapse, but the functional organization of these supramolecular nano-assemblies remains obscure. Electron tomography reveals the internal structure of synapses in three dimensions with exceptional spatial resolution. We here describe an approach to the study of ultrastructure that relies on plastic-embedded aldehyde-fixed material stabilized with tannic acid instead of osmium tetroxide. This approach offers a new window into the structural basis of synaptic processing in the mammalian brain.