Figure 3. Localization of Caspr in the outer plexiform layer. A: Immunostaining for Caspr (green) labeled an intense band in the outer plexiform layer (opl) as well as AII amacrine cells in the inner nuclear layer (inl) of mouse retina (Scale bar equal to10 μm). Double labeling with PKC (red) demonstrated co-localization with Caspr in the opl. Projection of 5 images totaling a stack thickness of 1.2 µm. B-D: Higher magnification images of Caspr (B), PKC (C) and overlay (D) of outlined region in A. Arrows in B, C indicate double labeled rod bipolar cell dendrites in the opl. Scale bar in D equal to 10 μm. E-G: High power images of double labeling for Caspr (E), Syx4 (F) and overlay in opl of mouse retina. Syx4 labels horizontal cell tips and densely labeled ‘sandwiches’ postsynaptic to cone pedicles (arrows, G). Note that Caspr labeling is largely not co-localized, and in several cases falls within a Syx4 sandwich. Large spots of labeling below opl in E are nonspecifically labeled blood vessels. Scale bar in G equal to 10 μm. Projection of 5 images totaling a stack thickness of 1.2 µm. H-J: Double labeling of Caspr (H) with Calbindin (I) and overlay (J) in tangential section through the opl in mouse retina. Arrowheads indicate horizontal cell processes double labeled with Caspr (H) and Calbindin (I). Scale bar in J equal to 25 μm.