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Date of Award
Kv4.2 is a fast activating, fast inactivating voltage-gated potassium channel that can be regulated by catecholamines, such as epinephrine and dopamine. It contributes to the transient IA current. Evidence suggests that Kv4.2 is differentially expressed in functional subtypes of retinal ganglion cells (RGCs), including those associated with the circadian cycle and form vision. This thesis determined how Kv4.2 contributes to IA and modulates the action potentials of these RGCs. Mouse retinas were acutely isolated and flat mounted on filter paper. Somas of single RGCs were current-clamped to assay action potentials and firing patterns and voltage-clamped to assay potassium current profiles. Potassium channel blocker BaCl2, which has been shown to block Kv4.2 currents in other types of neurons, was used to determine the role of currents on RGC action potential output. RGCs were then filled with dye and morphologically classified. Immunohistochemistry was used post hoc to determine whether recorded cells expressed Kv4.2. Kv4.2 was expressed at varying levels primarily in a small number of morphological subtypes. RGCs expressing Kv4.2 channels showed a greater reduction in IA current compared to RGCs not expressing Kv4.2 when exposed to bath application of BaCl2. In addition, BaCl2 decreased the current injection at which maximum firing frequencies occurred. This behavior demonstrates that Kv4.2-mediated currents regulate the action potential output in a distinct functional subset of RGCs and underlie a unique role for Kv4.2 currents in RGCs.
Devries, John Austin, "Kv4.2-Mediated Potassium Currents Modulate Action Potential Generation In Functional Subsets Of Retinal Neurons." (2010). Wayne State University Theses. Paper 8.