Figure 3.

Synaptic connection between photoreceptors and bipolar cells. (a) Immunolocalization of GluR1 (red) and PSD95 (green). In Cabp4^+/+ (left) and Cabp4^−/− (right) mice, GluR1 is expressed in off-cone bipolar cell dendrites²⁰ proximal to cone pedicles. PSD95 is localized proximal to the plasma membrane of the photoreceptor synaptic terminals. (b) Immunolocalization of mGluR6 (red) and PSD95 (green). A photoreceptor presynapse in a Cabp4^+/+ mouse shows morphologically distinguishable rod spherules and cone pedicles (arrows indicate cone pedicles). Cabp4^−/− mice have disorganized synaptic processes.(c) Immunolocalization of CaBP4 (red) and the presynaptic marker bassoon (green). Insets show higher-magnification images. (d) Immunolocalization of calbindin, a marker for H1 horizontal cells. Each picture is a three-dimensional projection made from multiple stacks of confocal images. (e,f) Three-dimensional projections of PKCα (red, a marker for rod bipolar cells) and PSD95 (green) immunolocalization in (e) Cabp4^+/+ and (f) Cabp4^−/− mice. Arrow indicates ectopic synapse in the outer nuclear layer between rod photoreceptor and bipolar cells. In a–f, nuclei were visualized by staining with Hoechst 33342 dye. Scale bars, 20 μm (in inset, 5 μm).