Centrifugal innervation of the neural retina has been described in all examined vertebrates including man. Previous studies have suggested a role of centrifugal input on retinal neural activity. However, how centrifugal signals influence overall visual performance such as rod and cone sensitivity and contrast remains unexplored. We have recently isolated a zebrafish mutation (night blindness b) that permits behavioral, physiological, and genetic studies of centrifugal innervation of visual sensitivity. The objective of this study is to understand the role of centrifugal input on visual sensitivity and to uncover the mechanism underlying the central nervous system centrifugal pathway. We use zebrafish (Danio rerio) as our model system. In zebrafish, the centrifugal pathway originates from terminalis neurons that are located in the olfactory bulb. In this proposal, experiments are designed to examine 1) the effect of olfactory input on cone and rod system sensitivity and contrast sensitivity, 2) the roles of olfactory input in outer and inner retinal neuronal activity, and 3) the mechanisms that underlie olfactoretinal centrifugal synaptic transmission. These studies will lend insights to retinal circuitry, particularly the one mediated by dopamine, and will provide fundamentals for better understanding of human visual functions and eye diseases.
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