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Activation of a Potassium Current by Rapid Photochemically Generated Step Increases of Intracellular Calcium in Rat Sympathetic Neurons

Gurney, Alison M. and Tsien, Roger Y. and Lester, Henry A. (1987) Activation of a Potassium Current by Rapid Photochemically Generated Step Increases of Intracellular Calcium in Rat Sympathetic Neurons. Proceedings of the National Academy of Sciences of the United States of America, 84 (10). pp. 3496-3500. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:GURpnas87

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Abstract

Although Ca2+ is a well-established intracellular messenger, there are many questions concerning the kinetics and spatial localization of its effects. Such problems may now be approached with the photosensitive Ca2+ chelator nitr-5. The Ca2+ affinity of this molecule decreases by a factor of 40 after absorption of near-UV light; Ca2+ is liberated with a time constant of approx 300 µs. Nitr-5 or the related compounds nitr-2 and nitr-7, complexed with Ca2+, were introduced into rat sympathetic ganglion cells by dialysis from a patch pipette electrode operating in the whole-cell, voltage-clamp mode. Light flashes released Ca2+ and activated a K+ current. Flash-induced current relaxations followed a simple exponential time course with time constants as brief as 5 ms. Comparison of the kinetics among the chelators, which photolyze at different rates, suggests that release of Ca2+ from nitr-5 is too fast to limit the relaxation. Thus we confirm directly that Ca2+ can modulate membrane properties within a few milliseconds after entering a cell. A preliminary kinetic description of K+ current activation by Ca2+ in rat sympathetic neurons is presented; Ca2+ appears to bind to the channel with a rate constant of at least 2 x 10^7 M^-1· s^-1.


Item Type:Article
Additional Information:Copyright © 1987 by the National Academy of Sciences Communicated by Melvin I. Simon, January 20, 1987 We thank Dr. S. Adams for synthesizing nitr-5 and nitr-7, Dr. J.M. Nerbonne for advice and helpful discussions, for participating in early experiments, and for providing facilities for some of the later experiments. We also thank Dr. C. Miller for a gift of charybdotoxin and for much discussion, Drs. P.R. Adams, R. Brett, S. Jones, J. Nargeot, and R. Zucker for discussion; and B. Tanamachi, D. Martin, and J. Doyle for preparing the cells. This research was supported by the American Heart Association Postdoctoral Fellowship to A.M.G., by Grant 83-K-111 from the Searle Scholars Program, by Grants GM-29836, GM-31004, and EY04372 from the National Institutes of Health, and by the Medical Research Council and British Heart Foundation. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Subject Keywords:light flash; calcium jump; superior cervical ganglion
Record Number:CaltechAUTHORS:GURpnas87
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:GURpnas87
Alternative URL:http://www.pnas.org/cgi/content/abstract/84/10/3496
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5805
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:02 Nov 2006
Last Modified:14 Nov 2014 19:19

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