Fig. 1.
Astrocytic profiles and 3D reconstructions illustrating their relationships to synapses in the middle of stratum radiatum of hippocampal area CA1. a, Astrocytic profiles are illustrated (blue) on a single thin section in the vicinity of 11 synapses (arrows). The identity of each of the astrocytic profiles occurring on this single EM section was confirmed by viewing serial sections. On this one section, three synapses have astrocytic profiles at their perimeters (arrowheads). To identify whether astrocytic processes occurred at the perimeter of the other synapses, they were viewed through serial sections, and four more of the synapses were found to have astrocytic profiles at their perimeters, for a total of seven.b–d, 3D reconstructions illustrate astrocytic profiles (blue), boutons (green), spines (gray), and PSDs (red). Astrocytic profiles surround (b) 50% of the perimeter of this macular synapse and (c) 3% of the perimeter of a perforated synapse, both occurring on SSBs. In d, three synapses occur with a single presynaptic bouton, called a multiple synapse bouton, and a single astrocytic process surrounds 75, 64, or 100% of the perimeter of each synapse fromleft to right, respectively. Scale bars: 1 μm (shown in b for b–d).