Figure 2. Retinal muscarinic receptor subtype protein expression in the tree shrew. Tree shrew posterior eye cups were fixed in 4% paraformaldehyde and reacted with muscarinic monoclonal antibodies to their respective receptor subtypes. A FITC-labeled secondary antibody was used to visualize the protein distribution in the retina (first column). The corresponding bright-field section (second column) and negative controls (last column) are also shown. The layers of the retina are highlighted, and the scale bar represents 20 μm. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer; NFL, nerve fiber layer.