Fig. 1.

Triple-labeled retina with a Neurobiotin-injected AII amacrine cell. A: Confocal section of the retina in the plane of ON bipolar cells. The somas of all depolarizing bipolar cells were labeled with G_0α (green). This includes all rod bipolar cells as well as ON cone bipolar cells. Rod bipolars (labeled “R”) are labeled with PKCα (blue). The coupled ON cone bipolar cells (labeled “C”) are filled with Neurobiotin (red). The injected AII cell (upper right, labeled “I”) is in a different plane but had z-blur visible in this level. Likewise, the z-blur of other AII amacrine cells is marked with an “A.” Cells that were found to be labeled with G_0α but nothing else (green outlined cell with no fill) were identified as noncoupled ON cone bipolars and labeled with an asterisk. In this tissue we found 62 rod bipolar cells, 16 AII amacrine cells, 46 coupled ON cone bipolar cells, and 18 noncoupled ON cone bipolar cells. Approximately 28% of ON cone bipolars were noncoupled. B: Normalized average image of noncoupled ON cone bipolar cells (see Materials and Methods). Note the G_0α (green) ring that excludes PKCα and Neurobiotin in its center, indicating that these ON cone bipolars contained no Neurobiotin. C: Normalized average image of coupled ON cone bipolar cells. The red channel has the inverse distribution of B. D: Same as C, but with red channel removed for comparison. Scale bar = 20 μm in A; 5 μm in B–D.