Figure 2.

a: Cone photoreceptors extend axons through the outer nuclear layer to reach the innermost stratum of the OPL where they form a periodic distribution of pedicles across the retina, labeled with PNA (blue in panel d), viewed here in a wholemount preparation. b: Type 7 cone bipolar cells, brightly labeled (green in panel d) due to a gustducin-GFP reporter transgene, extend their dendritic fields to contact the pedicles in the presence of numerous homotypic neighbors. Other heterotypic neighbors, including the rod bipolar cells (expressing the gustducin-GFP transgene weakly, and hence dimly labeled), also extend dendrites into the OPL, receiving innervation from the rod spherules (unlabeled herein) distributed through the full depth of the OPL. c: Each cone pedicle innervates nearly every type of cone bipolar cell, as well as one other post-receptoral neuron, the horizontal cell, the somata and processes of which are immunolabeled for calbindin (red in panel d). d: Superposition of all three labels: cone pedicles are shown in blue, bipolar cells in green, and horizontal cells in red. Calibration bar = 25 μm.