Fig. 3

Neuronal and astrocytic process elaboration follows a similar timeline as synapse development. a Representative 3-D rendering of layer V rat SSC neurons reconstructed from biocytin-labeled neurons at different ages as labeled (dendrites in red, axons in blue). At P14, 21 and 36 the axons are shown cropped due to space limitations. Scale bar = 200 μm. Adapted with permission from [131]. b Representative images of Lucifer yellow filled rat hippocampal astrocytes at different developmental stages as indicated in each panel. Astrocyte process ramification increases with age. Scale bars = 5 μm. Adapted with permission from [67]. c Development of synapses in the mouse visual cortex visualized by electron microscopy at the different developmental ages as labeled. At P0 neurotransmitter vesicles can be visualized, but the postsynaptic density is not present. At P7, P21 and P30 presynaptic terminals with neurotransmitter vesicles apposed to postsynaptic density structures, marking synaptic contacts, are shown. Asterisk at P30 indicates immunoreactivity for the presynaptic marker synaptophysin. Scale bar = 130 nm. Adapted with permission from [84]