Do cone bipolar cells express punctate immunoreactivity for the ρ subunits?
Punctate immunofluorescence within the IPL (Figs. 3, 4) is not restricted to the inner part where RB cells terminate, but exists across the entire IPL. This suggests localization of the puncta not only on RB cell axon terminals, but also on cone bipolar (CB) cell axon terminals. Most of the markers, such as recoverin, that specifically label CB cells of the rat retina (Milam et al., 1993; Euler and Wässle, 1995) could not be applied here because they were raised in the same species (rabbit) as the ρ1 antibodies. Therefore, we addressed this question for the macaque monkey retina, where PKC immunoreactivity is found in RB cells and in the type DB4 cone bipolar cell (Grünert et al., 1994). A vertical section through parafoveal monkey retina is shown in Figure6 A. Strong labeling of RB cell dendrites in the OPL, of RB cell perikarya in the INL, and of RB cell axon terminals at the inner margin of the IPL is apparent. However, as indicated by the two horizontal arrows in Figure 6 A, there
