P-Rex2 is expressed in rod bipolar cell terminals. A-C: Widefield microscopy of double labeling for P-Rex2 and Protein kinase C (PKC), a rod bipolar cell marker. A: P-Rex2 is present in photoreceptor terminals in the OPL and in numerous bipolar cell terminals in the IPL. B: Labeling for PKC identifies rod bipolar cells (RB) and their terminals in the innermost portion of the ON sublamina of the IPL (arrowheads). C: The overlay of panels A and B shows that P-Rex 2 is localized to rod bipolar cell terminals in the IPL. Rod bipolar cell dendrites in the OPL did not show P-Rex2 labeling. D-F: Confocal imaging of P-Rex2 and PKC labeling in the IPL confirms that P-Rex2 (panel D) is localized to rod bipolar cell terminals (arrowheads) labeled for PKC (Panel E). There is little labeling for P-Rex2 in the axons of the rod bipolar cells coursing through the IPL. Panel F shows the overlay of panels D and E. Single optical plane of approximately 0.3 μm thickness shown. Nuclei are counterstained with DAPI (blue) in panels A and D to illustrate the locations of the nuclear layers. ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bars = 20 μm for A-C; 10 μm for D-F.