Microglia and Synapse: Interactions in Health and Neurodegeneration
Figure 5
Three-dimensional reconstructions of degenerating synapses in the stratum radiatum of hippocampus in prion disease. (a) Rotations of a synaptic profile generated from 46 consecutive sections; the material originating from the presynaptic terminal (in blue) remains outside and inside (engulfed by the PSD (in red)) of the dendritic spine (in purple). Note the presence of one astrocytic process (in yellow) in proximity but not engaged with the degenerating terminal. The first 24 consecutive sections, from which the profile was generated, are illustrated in (c). (b) Rotations of a synaptic profile from 20 consecutive sections. The presynaptic element (in blue) appears internalized by the dendritic spine head (in orange); however, a fine strand of material originating from the presynaptic element remains in association with the extracellular space and is not within the encircling PSD of the spine. (c) Electron micrographs of serial sections illustrating a degenerating synaptic terminal in the stratum radiatum neuropil. The cytoplasm of the presynaptic element (in blue) is electron-dense in all sections; although the synaptic vesicles are still visible, the presynaptic element is disconnected from the projecting axonal terminal and remains arrested and almost completely engulfed by the PSD (in red) of the dendritic spine (in purple). A process of one astrocytic cell (in yellow) is in close proximity. Scale bar: 1000 nm. Reproduced from Šišková et al. [89].
