Amount of postsynaptic receptors scales with overlap between bipolar cell dendrites and cones. Examples of type 6 cone bipolar cell dendrites at (**a**) P14, (**b**) P30, and (**c**) P172. Single image plane of type 6 bipolar cell dendrites alone (first column). Single image plane of bipolar cell dendrites (red) and a cone (blue) (second column) and with mGluR6 (yellow) within bipolar cell dendritic masks (third column). Location of the single plane is indicated by the dotted lines in the fourth column. Side view of a stack of planes located in between the dotted lines in the third column (fourth column). In the single plane view, the bipolar cell dendrites invaginate the cone at punctate locations, indicated by the white arrowheads. These punctate dendritic endings coincide with mGluR6 labeling. (**d**) Summary of volume overlap among bipolar cell dendrites, cones, and mGluR6 (three-way overlap) against volume overlap between bipolar cell dendrites and cones (two-way overlap) for different ages. Data points fit with line. (**e**) Number of cones contacted using volume overlap between bipolar cell and cones (2-way; closed circles) and among bipolar cell, cones, and mGluR6 (3-way; open diamonds) for the same dataset. A paired t-test was used to compare the number of cones contacted at each age for 2-way and 3-way volume overlap criteria. The null hypothesis could not be rejected for all comparisons: type 6 *p* > 0.47 [*n* = 9 (P14), 21 (P21), 13 (P30), 14 (P69), 12 (P123), 11 (P172)], type 7 *p* > 0.46 [*n* = 9 (P14), 12 (P21), 11 (P30), 8 (P69), 3 (P172)], type 8 *p* > 0.05 [*n* = 7 (P14), 11 (P21), 11 (P30), 7 (P69), 6 (P172)]. Scale bar, 1 μm.

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