Figure 4.

Organization of postsynaptic and dendritic structures within synaptic clusters. (A) Co-immunolabeling with antibodies against PSD-95 (Left, green) and synapsin I (Middle, red) reveals the postsynaptic counterpart to presynaptic clusters detected with FM1–43. Superimposition of both staining patterns depicts the spatial correlation between the two markers within a cluster (Left). (B) GFP-labeled apical dendrite of a pyramidal cell (Left, green) and the localized synaptic clusters labeled with FM4–64 (Right, red) that surmount the dendrite. Note the co-localization of FM4–64 staining with branches and spines originating from the parent dendrite. Scale bar applies to both panels. (C) Complex dendritic arborizations penetrate the synaptic clusters as indicated by monoclonal antibody staining for MAP-2, a dendritic marker. The upper panel shows top view of a three-dimensional reconstruction obtained from 20 confocal sections through the synaptic cluster (2 μm thick optical slices); the bottom panel shows a side view of the same dendritic structure. (D) Co-staining with antibodies against MAP-2 (green) and synaptotagmin I (red) shows correspondence between large dendritic arborizations and synaptic markers.