Developmental expression of synaptophysin, synapsin I and syntaxin in the rat retina

Expression of synaptophysin, synapsin I and syntaxin was studied immunocytochemically in the developing rat retina using indirect immunoperoxidase technique. In the inner plexiform layer (IPL), syntaxin immunoreactivity appeared at postnatal day 1 (P1) whereas synaptophysin and synapsin I staining were first observed at P2. In the outer plexiform layer (OPL), synaptophysin appeared at P4, while synapsin I and syntaxin appeared at P8. In the case of synaptophysin, a punctate pattern of staining was observed from the time of its appearance (P4) in the OPL and from P12 onwards in the IPL. Synapsin I and syntaxin immunoreactivity in the OPL were of a low intensity throughout the development and in the adult stage. These findings are discussed in relation to synaptogenesis in the rat retina.