The overall objective of this proposal is to learn the mechanisms by which graded, and in particular, mild hypoxia alters the functional interactions between the neural retina and the retinal pigment epithelium (RPE). Recent experiments in the intact cat retina and in my preliminary in vitro results have demonstrated that quite mild levels of hypoxia affect potassium homeostasis in the subretinal space and the potentials of the RPE. In vitro models of the gecko retina will be developed to investigate the origins and cellular mechanisms of these hypoxic effects. Specific experiments will determine the relative roles of photoreceptors, RPE and Muller cells in 1) a hypoxia-induced increase in steady-state potassium in the dark; 2) hypoxia-induced changes in the amplitude and time-course of light-evoked potassium responses; and 3) hypoxia-induced changes in apical and basal membrane potentials and conductances both in the dark and in response to light. The strategy will be to study hypoxic responses in the isolated retina and isolated RPE preparations to distinguish effects on photoreceptor and RPE cells. Intracellular recordings will be used to record effects of hypoxia on membrane potential and conductance; potassium-selective microelectrodes will be used to explore effects of hypoxia on potassium. A new electrophysiological technique has been developed to study the RPE sodium-potassium pump. The gecko retina has been shown to be a good model for normoxic responses from the intact cat eye. Since the cat is a good model for human, results form this in vitro hypoxic model should apply to human. Little is known about the primary effects of graded hypoxia on neurons or epithelia in general, or specifically on the photoreceptors and RPE, so that the proposed research will be of significance to both basic and clinical science.
