Syntaxin 3 does not colocalize with syntaxin 1. A–C: Syntaxin 3 is localized to the glutamatergic photoreceptor terminals in the outer plexiform layer (OPL) and numerous bipolar cell terminals in the inner plexiform layer (IPL). Labeling is also present in the cell bodies and inner segments of the photoreceptors and in bipolar cell bodies and axons. Syntaxin 1 labeling is restricted to amacrine cells and amacrine cell processes. Images shown from a projection of 10 optical sections with total thickness of 1.93 μm. Box indicates area shown in panels D–F. D–F: Examination of syntaxin 3 and syntaxin 1 immunolabeling at higher magnification confirms that these syntaxin isoforms are present in different sets of synaptic terminals. Arrows indicate bipolar cell terminals labeled for syntaxin 3. Images shown from a projection of 15 optical sections with total thickness of 2.04 μm. IS, inner segments; ONL, Outer nuclear layer; INL, inner nuclear layer, GCL, ganglion cell layer. Scale bars = 20 μm for A–C; 10 μm for D–F.