This project aims to determine the principal factors governing the transfer of information from retinal photoreceptors to bipolar cells.
Specific aims i nclude i) to evaluate the sources of noise that limit the signal-to-noise ratio of the process of signal transfer, ii) to establish which classes of ionic channels are modulated by synaptic transmitter, iii) to determine the electrical properties of the bipolar cell membrane and to study the spatial distribution of conductance over the surface of the bipolar cell, iv) to determine the mechanism responsible for the band-pass filtering of the rod/bipolar cell synapse and v) to incorporate these findings into a comprehensive picture of the transfer of a signal from the receptor to the bipolar cell's axon terminal. We have concentrated so far on the transfer of weak signals initiated by rods following absorption of only a few photons since this permits a linear systems analysis to be carried out. We plan to continue, at least initially, with this approach. A new facet of the work will be a study of enzymatically dissociated cells studied under voltage clamp. This will be set against a background of similar experiments on bipolar cells in the intact, isolated retina and an ongoing electron-microscopic study of the functional morphology of these cells. An analysis of the voltage gain of synaptic transfer between receptors and bipolar cells will be tested. This project should add considerably to our understanding of the process of signal transfer, not only in the retina but in the nervous system in general. It should provide information contributing to our knowledge of visual function at very low luminances and may contribute to an understanding of certain clinical disorders involving low-vision loss.
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