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This Article Full Text Full Text (PDF) All Versions of this Article: 97/6/4225    most recent 01022.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kaneda, M. Articles by Shimoda, Y. Search for Related Content PubMed PubMed Citation Articles by Kaneda, M. Articles by Shimoda, Y.

Characterization of Voltage-Gated Ionic Channels in Cholinergic Amacrine Cells in the Mouse Retina

¹Department of Physiology, Keio University School of Medicine, Tokyo; ²Department of Comparative Pathophysiology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo; ³Department of Biological Sciences, Faculty of Medicine, Kyoto University, Kyoto; and ⁴Medical Research Institute, Tokyo Women's Medical University, Tokyo, Japan

Submitted 25 September 2006; accepted in final form 2 April 2007

Recent studies have shown that cholinergic amacrine cells possess unique membrane properties. However, voltage-gated ionic channels in cholinergic amacrine cells have not been characterized systematically. In this study, using electrophysiological and immunohistochemical techniques, we examined voltage-gated ionic channels in a transgenic mouse line the cholinergic amacrine cells of which were selectively labeled with green fluorescent protein (GFP). Voltage-gated K⁺ currents contained a 4-aminopyridine-sensitive current (A current) and a tetraethylammonium-sensitive current (delayed rectifier K⁺ current). Voltage-gated Ca²⁺ currents contained a -conotoxin GVIA-sensitive component (N-type) and a -Aga IVA-sensitive component (P/Q-type). Tetrodotoxin-sensitive Na⁺ currents and dihydropyridine-sensitive Ca²⁺ currents (L-type) were not observed. Immunoreactivity for the Na channel subunit (Pan Nav), the K channel subunits (the A-current subunits [Kv. 3.3 and Kv 3.4]) and the Ca channel subunits (1_A [P/Q-type], 1_B [N-type] and 1_C [L-type]) was detected in the membrane fraction of the mouse retina by Western blot analysis. Immunoreactivity for the Kv. 3.3, Kv 3.4, 1_A [P/Q-type], and 1_B [N-type] was colocalized with the GFP signals. Immunoreactivity for 1_C [L-type] was not colocalized with the GFP signals. Immunoreactivity for Pan Nav did not exist on the membrane surface of the GFP-positive cells. Our findings indicate that signal propagation in cholinergic amacrine cells is mediated by a combination of two types of voltage-gated K⁺ currents (the A current and the delayed rectifier K⁺ current) and two types of voltage-gated Ca²⁺ currents (the P/Q-type and the N-type) in the mouse retina.

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