Single immunofluorescent images of Nlgn3 (green) in the whole brain (A and D), hippocampal formation (B and E), and CA1 region (C and F) of P21 wild-type (A–C, WT) and Nlgn3 knockout (D–F, Nlgn3-KO) mice. Nissl staining is magenta. Higher levels are detected in the cortex (A, Cx), striatum (A, St), olfactory bulb (A), (OB), and hippocampal formation (A–C, Hi). In the hippocampus, intense labeling is noted in the st. lacunosum-moleculare (LM) of Ammon's horn and in the molecular layer (Mo) of dentate gyrus (B). This staining is not detected in Nlgn3-KO mice (D–F). (G) The noise levels for intensities and co-localizations of Nlgn3 signals obtained from immunofluorescent images for Nlgn3 (green), VIAAT (blue), and interneuron markers (red) including VGT3, CB1, Pv, and Sst with the Nlgn3 channel rotated 90°. Arrows indicate inhibitory synapses co-labeled with VIAAT and different interneuron markers. CA1–3, CA1–3 regions of the Ammon's horn; Cb, cerebellum; Cx, cerebral cortex; DG, dentate gyrus; Gr, granule cell layer; Hi, hippocampus; Mb, midbrain; MO, medulla oblongata; OB, olfactory bulb; Or, st. oriens; Py, pyramidale; Ra, st. radiatum; St, striatum; Th, thalamus. Scale bars, 1 mm (A and D), 500 µm (B and E), 5 µm (C and F), and 2 µm (G).