Syntaxin 4 does not colocalize with the presynaptic active zone protein, bassoon, in the inner plexiform layer (IPL). A–C: Syntaxin 4-positive puncta in the IPL (arrowheads) do not show colocalization with presynaptic active zones containing bassoon (arrows). However, close apposition of syntaxin 4-positive puncta and bassoon-containing active zones is present (circles). Single confocal plane shown. Scale bars = 10 μm.