Neurons of the vertebrate retina will be studied in a preparation of isolated cells maintained in cell culture. The overall goal of the project is to determine how the individual neurons of the vertebrate retina process visual information. The techniques of whole-cell and single-channel voltage-clamp will be used to characterize the voltage and neurotransmitter gated ionic currents intrinsic to the membranes of retinal horizontal, bipolar and ganglion cells. Specifically, the neurons will be voltage- clamped and potassium and calcium currents investigated. I-V characteristics will be studied as well as gating, kinetics of currents, activation and inactivation. Single channel recordings will be carried out to investigate the properties of retinal potassium and calcium channels and to make comparisons with those types of channels found in the CNS. Putative photoreceptor neurotransmitters such as glutamate, kainate and quisqualate will be studied in an effort to determine how these transmitters modulate the membrane properties of horizontal and bipolar cells. For similar reasons, the actions of putative amacrine cell transmitters on ganglion cells will be studied. The modulation of electrical coupling between horizontal cells will also be investigated using these techniques. The use of isolated retinal neurons is a powerful tool which allows the study of the physiology of retinal cells outside of the retinal network. Problems such as the state of light adaptation and indirect effects of neurotransmitters due to a multiplicity of inputs are not present. As a result, information can be gathered which was previously inaccessible. This project will provide knowledge about the basic properties of ionic channels in retinal cell membranes and how these channels are modulated to influence the signalling capabilities of the cell. This will lead to a better comprehension of how retinal neurons operate, as well as an increased understanding of how the nervous system in general processes information.
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