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dc.contributor.authorWelch, Nicole Cheryl.en_US
dc.date.accessioned2014-10-21T12:33:31Z
dc.date.available2014-10-21T12:33:31Z
dc.date.issued2005en_US
dc.identifier.otherAAINR00959en_US
dc.identifier.urihttp://hdl.handle.net/10222/54688
dc.descriptionMuller cells are the principal glial cells of the vertebrate retina and perform a number of functions vital to retinal integrity, some of which require electrical activity. In this study, ion channels in freshly isolated salamander Muller cells were identified and studied using electrophysiological, immunocytochemical and fluorescent imaging techniques.en_US
dc.descriptionHigh-voltage-activated (HVA) Ca channel currents were found to activate positive to -30 mV in acutely isolated Muller cells. These currents were partially sensitive to L-type Ca channel blockers. Imaging techniques showed that L-type Ca channels were localized broadly over the Muller cell membrane and not segregated to individual regions. HVA Ca channel currents were highly sensitive to the N-type Ca channel blocker, o-conotoxin GVIA, but were only modestly blocked by o-agatoxin IVA, a P/Q-type Ca channel blocker. Immunochemistry revealed that while N-type Ca channels were widely distributed throughout all regions of the Muller cell, P/Q-type Ca channels were found only in the apical processes. The observations suggest the presence of either a mixed population of Ca channel subtypes or a single, unconventional HVA Ca channel subtype sharing several Ca channel characteristics.en_US
dc.descriptionA calcium-activated potassium (KCa) channel current recorded in Muller cells was enhanced by the application of A23187, a Ca 2+ ionophore, and blocked by iberiotoxin, a specific blocker of large-conductance KCa channels. TEA also reduced this current. Cd2+ had only a small blocking effect on KCa channel currents suggesting that Ca2+ influx through voltage-gated Ca channels is not the principal means of activation. KCa channel activation was sensitive to release of Ca2+ from intracellular stores.en_US
dc.descriptionIonomycin, a Ca2+ ionophore, activated a Ca2+-activated Cl (ClCa) channel current. ClCa channel currents were abolished by Cd2+ and enhanced by depolarization indicating that channel activation was sensitive to Ca2+ influx through voltage-dependent Ca channels. ClC-3 channels, which are reportedly Ca 2+ sensitive, are also expressed in Muller cells. Using antibody dialysis, ClC-3 was shown not to contribute to ClCa channel currents. Immunochemistry revealed that ClC-3 was localized to intracellular organelles and was not at the plasma membrane of Muller cells.en_US
dc.descriptionThese studies identified voltage-dependent Ca and Ca-dependent ion channels that contribute to Muller cell electrogenic processes. Knowledge of the biophysical properties and regulation of these ion channels increases our understanding of the function of Muller cells in the retina.en_US
dc.descriptionThesis (Ph.D.)--Dalhousie University (Canada), 2005.en_US
dc.languageengen_US
dc.publisherDalhousie Universityen_US
dc.publisheren_US
dc.subjectBiology, Neuroscience.en_US
dc.subjectBiology, Cell.en_US
dc.subjectHealth Sciences, Pharmacology.en_US
dc.titleCalcium-dependent ion channels of retinal Muller glial cells.en_US
dc.typetexten_US
dc.contributor.degreePh.D.en_US
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