This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Retinal photoreceptors are specialized structures where light is transformed into the neural signal that leads to sight. A major building block of photoreceptor membranes is DHA (docosahexaenoic acid, 22:6n-3), a highly polyunsaturated n 3 fatty acid. In our previous studies, rhesus monkeys fed low levels of n-3 fatty acids during development had reduced retinal DHA, impaired visual acuity development and changes in retinal function. Similar effects were found in human infants fed formulas low in n-3 fatty acids. DHA also is low in the blood and tissues of human patients with retinitis pigmentosa, and dietary DHA is being tested as a therapeutic treatment for this blinding disease. However, the mechanisms underlying changes in retinal function associated with altered fatty acid composition are poorly understood. We examined retinal function in rhesus monkeys raised on diets with different levels of n-3 fatty acids shown to result in widely differing retinal DHA levels. We developed new noninvasive methods to measure photoreceptor cell activity, and used them to define effects on critical steps in the visual process, including: the time course of the rod photoresponse, including the time constants of activation and deactivation; the desensitization of the rod response by light adaptation; and the kinetics of dark adaptation. These studies are helping to determine the processes altered by differing retinal fatty acid composition. They also contribute to understanding the changes in retinal function found in human infants fed diets low in n-3 fatty acids.
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