Synaptic basis of rod-cone interaction in the vertebrate retina.
Item
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Title
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Synaptic basis of rod-cone interaction in the vertebrate retina.
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Identifier
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AAI8820859
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identifier
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8820859
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Creator
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Eysteinsson, Thor.
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Contributor
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Adviser: Thomas E. Frumkes
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Date
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1988
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Physiological
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Abstract
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Frumkes and Eysteinsson (1987) described a type of rod-cone interaction in amphibian retina which they called suppressive rod-cone interaction (SRCI). The intracellular response from most types of retinal neurons was obtained in response to spatially focal stimuli flickering at frequencies {dollar}>{dollar}4 hz which amphibian rods cannot follow; therefore, the flicker response reflects cone activity. Dim, spatially diffuse, rod-stimulating backgrounds enhance flicker responsiveness by as much as 800%. Frumkes and Eysteinsson attributed this effect to a tonic inhibitory influence of the cones upon the horizontal cells (HCs) which is removed by selective light adaptation.;The synaptic basis for SRCI was investigated by means of intracellular recording from retinal neurons in the superfused eyecup of the mudpuppy, Necturus maculosus. In the distal retina, specific synaptic actions were evaluated by superfusing pharmacological agents with delimited, well characterized effects. Amino acid analogues which selectively block the photic response of HCs (e.g., D-O-Phosphoserine (COP), Kynurenic Acid (Kya)) block SRCI in cones and bipolar cells. Lead chloride, which selectively blocks the rod input into horizontal cells, blocks SRCI. All these agents enhance the amplitude of the flicker response to levels only seen in the presence of an adapting field. These results are consistent with the model. In contrast, 2-amino-4-phosphonobutyric acid (APB), which blocks the photic response of depolarizing bipolar cells, has no influence upon SRCI in HCs or Off-cells. 1 mM Dopamine reduces electrical coupling between HCs and has little influence upon flicker responsiveness in the dark, but reduces background enhancement of flicker in horizontal and bipolar cells, suggesting that SRCI may depend upon HC electrical coupling.;Some sustained ON- and OFF-ganglion and amacrine cells display SRCI. DOP, and KyA have a similar effect to that observed in bipolar cells, suggesting that SRCI merely reflects an expression of an outer plexiform layer circuit. But SRCI in OFF amacrine and ganglion cell was in some cases enhanced by APB, indicating that SRCI in the distal retina is further modified by inner plexiform layer circuitry.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
