The synapse between photoreceptors and OFF bipolar cells - molecular mechanism of parallel processing of visual signals

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The synapse between photoreceptors and cone bipolar cells is the first synapse of the visual system. The temporal and spatial pattern of activity of the photoreceptor array constitutes the primary representation of visual information, which is transformed into a gradual signal by modulating exocytosis of glutamate, and it is eventually distributed to different bipolar cell channels operating in parallel. For this purpose, the highly specialized ribbon synapse has evolved. In this research proposal we will investigate pre- and postsynaptic parameters crucially determining the transfer function(s) at this particular synapse. Presynaptically, we will focus on the role of an intact ribbon structure as well as on the kinetics of vesicle release. On the postsynaptic site, the subunit composition of glutamate receptors in combination with varying diffusion distances will be investigated. These parameters shape the amplitude and kinetics of the postsynaptic response and thus are fundamental for encoding visual information within the retinal network.