The characterization and physiology of on- and off-bipolar cells in the skate (Raja erinacea) by whole cell patch clamp analysis.
Item
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Title
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The characterization and physiology of on- and off-bipolar cells in the skate (Raja erinacea) by whole cell patch clamp analysis.
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Identifier
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AAI3047258
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identifier
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3047258
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Creator
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Rosenstein, Frederick J.
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Contributor
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Adviser: Richard L. Chappell
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Date
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2002
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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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Biology, Neuroscience
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Abstract
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This investigation of the skate (Raja erinacea) all-rod retina has identified, through electroretinogram (ERG) and whole-cell voltage clamp recording, independent ON and OFF afferent pathways in outer retina that are attributed to two types of bipolar cells. ON and OFF components of the ERG response could be selectively suppressed with targeted blocking agents. The application of L-2-amino-4-phosphonobutyrate (APB) to block the ON pathway plus picrotoxin (PTX) to inhibit GABAergic input left a functional OFF response that could be suppressed with a solution of APB, PTX plus 4-hydroxyquinoline-2-carboxylic acid (kynurenic acid (KYN)). N-methyl-D-aspartate (NMDA), known to be an inner retina blocker, when added to the solutions had no observable effect on the ON and OFF responses. These results suggested the presence of ON and OFF bipolar cells.;Through a comparative study of isolated bipolar cells, using glutamate specific agonists, in conjunction with whole-cell voltage clamp recording, ON and OFF bipolar cells were identified. Skate ON bipolar cells have metabotropic glutamate receptors that are responsive to the agonists APB and trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD), while the OFF bipolar cells have ionotropic glutamate receptors responsive to the agonists kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The reversal potential for both cell types are near 0mV and their currents are in opposite directions to each other at positive and negative holding potentials.;In a secondary study, zinc superfused in conjunction with glutamate onto bipolar cells greatly suppressed glutamate-mediated currents in both ON and OFF bipolar cells. Supporting evidence was garnered from ERG experiments. The ON and OFF pathways were isolated with PTX and then using histidine (HIS) as a zinc chelating agent, a solution of PTX plus HIS caused the ON response to become larger. The effect is consistent with findings from isolated bipolar cells. Zinc has an inhibitory effect on the glutamatergic responses in ON and OFF bipolar cells, and chelating zinc would reduce such action. An important conclusion from this ERG experiment is that endogenous zinc in the retina has a neuromodulatory effect in the intact retina.
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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.
