Syntaxin 4 in the inner plexiform layer (IPL) is not associated with ganglion cell dendrites or with Müller glial cell processes. A–C: Double labeling for syntaxin 4 and the ganglion cell dendrite marker, MAP 1. Syntaxin 4-positive puncta (arrows) form a plexus along the inner nuclear layer (INL)/IPL border with a few puncta present more proximally in the IPL. Ganglion cell dendrites labeled for MAP-1 are present throughout the thickness of the IPL, but do not show syntaxin 4 labeling. Contact between syntaxin 4-positive puncta and ganglion cell dendrites is seen only rarely (arrowheads). Images shown from a projection of 24 optical sections with total thickness of 3.35 μm. D–F: Double labeling for syntaxin 4 and glutamine synthetase (GS), a marker for Müller glial cells, shows no colocalization of syntaxin 4-positive puncta in the IPL (arrowheads) or in the outer plexiform layer (OPL; arrows). Images shown from a projection of 14 optical sections with total thickness of 3.35 μm. OLM, outer limiting membrane; ONL, outer nuclear layer; GCL, ganglion cell layer. Scale bars = 10 μm for A–C; 20 μm for D–F.