Figure 5. Weak VAMP-1-immunoreactivity in the OPL is associated with photoreceptor terminals

A-C: Double-labeling for VAMP-1 and VGLUT1, a marker for photoreceptor terminals in the OPL. Labeling for VAMP-1 colocalizes with labeling for VGLUT1, indicating that VAMP-1 labeling in the OPL is associated with photoreceptor terminals. D-F: Double-labeling for VAMP-1 and calbindin (CaBP), a marker for horizontal cells (H). The two labels do not colocalize. Labeling for VAMP-1 is located distal to CaBP labeling in the horizontal cell processes in the proximal OPL, consistent with expression of VAMP-1 in photoreceptor terminals rather than the dendrites of second-order neurons. Scale bars represent 10 μm.