Functional development of signal transmission at cone photoreceptor ribbon synapses in mouse retina

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Photoreceptors are specialized sensory neurons that transduce light signals into electrical and further into chemical signals. To ensure signal transmission with highest fidelity to postsynaptic horizontal and bipolar cells, photoreceptors are equipped with a so-called ribbon synapse, a synapse that is specialized for the fast and high-throughput graded release of glutamate. The understanding of the physiological properties of the synaptic machinery of photoreceptors is a central issue in visual neuroscience. In the proposed project, I will employ electric stimulation of photoreceptors in horizontal retinal slices to trigger synaptic vesicle release, a technique developed in our laboratory. Electric stimulation in combination with patch-clamp recording from horizontal cells will allow me to investigate the postnatal development of key physiological properties of photoreceptor ribbon synapses in mouse retina. I will analyse both tonic and phasic evoked synaptic vesicle release, measure the kinetics of synaptic vesicle release and replenishment, determine the readily releasable synaptic vesicle pool size, and measure presynaptic Ca2+ currents in patch clamped cone photoreceptors. In addition, I will study the changes in synaptic ultrastructure during postnatal development in order to correlate ribbon synaptic function with synaptic structure. The results of this study will establish the relationship between structure and function during photoreceptor ribbon synaptic development, enabling a better understanding of the physiology and pathophysiology of photoreceptor ribbon synapses in the mature mammalian retina.