Sema3A expression in PNN. Confocal microscopy shows Sema3A immunoreactivity (green) which surrounds the somatodendritic compartment of an interneuron in the rat neocortex. Sema3A staining displays a honeycomb-like pattern which is typical for the structure of PNNs (a)–(c). Colabeling with the presynaptic marker SV2 (red) reveals that synaptic boutons on the neuron surface fill the holes in the Sema3A-positive honeycomb-like structure of the PNN ((d)–(f), arrows). The Sema3A receptor component PlexinA4 (green) is closely associated with the Sema3A (red) positive net. Like Sema3A, PlexinA4 (arrowheads) is not present in the holes (asterisks) of the honeycomb-like structure of the PNN (g)–(i). Scale bar for (a)–(c) is 20 µm; for (d)–(f) is 8 µm; for (g)–(i) is 3.5 µm.