Figure 6. Small, weak CFP fluorescent somata in the INL and GCL contain HPC-1 immunoreactivity, a marker of amacrine and displaced amacrine cells. A: A transverse section of peripheral retina shows cyan fluorescent protein (CFP) expression in numerous somata in the ganglion cell layer (GCL) and weak CFP-expressing somata in the proximal inner nuclear layer (INL). B: Same section as in A shows syntaxin 1a (HPC-1) immunoreactivity in amacrine and displaced amacrine cell somata in the INL and GCL, respectively. HPC-1 immunostaining is very strong in the inner plexiform layer (IPL) and the weaker HPC-1 immunoreactive somata in the GCL tend to be obscured in transverse sections. C: A merged image of A and B shows colocalization of CFP and HPC-1 immunoreactivity in small, weakly CFP-expressing cell bodies in the INL and GCL. The scale bar for A-C is 40 μm. D: A higher magnification image of transverse retina shows CFP fluorescence in ganglion cells in the GCL and in smaller, weakly CFP fluorescent cells in the INL and GCL (arrows). E: The same section as in D shows HPC-1 immunoreactivity in numerous amacrine and displaced amacrine cell somata in the INL and GCL (arrows). F: A merged image of D and E shows colocalization of CFP expression and HPC-1 immunoreactivity in amacrine and displaced amacrine cells (arrows) in the INL, and GCL. The scale bar for D–F is 25 μm. G: CFP is localized to brightly and weakly fluorescent cell bodies of various sizes in the GCL. Image is from a retinal wholemount located 1.5 mm from the optic nerve head in midperipheral nasal retina. H: Same region as in G shows HPC-1 immunoreactivity in numerous cell somata in the GCL. I: A merged image of G and H shows the colocalization of CFP and HPC-1 immunoreactivity in displaced amacrine cell bodies in the GCL (arrows). The scale bar for G-I is 30 μm. In C and F outer plexiform layer is abbreviated outer plexiform layer (OPL).