Syntaxin 1 is associated with conventional synapses in the inner plexiform layer (IPL). A–C: Confocal microscopy of double labeling for syntaxin 1 and synapsin I, a marker for conventional synapses made by amacrine cells. There is appreciable colocalization of labeling in conventional synaptic terminals (arrows). However, syntaxin 1 labeling is not restricted the presynaptic terminal and is often seen independent of synapsin I labeling. Box indicates area shown in panels D–F. D–F: Examination of syntaxin 1 and synapsin I double labeling from the area indicated by the box in panels A–C confirms the localization of syntaxin 1 to conventional synapses. GCL, ganglion cell layer. Images shown from a projection of 12 optical sections with total thickness of 1.6 μm. Scale bars = 10 μm for A–C; 5 μm for D–F.