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      Acetylcholine, Ca 2+ Overload and Oscillatory Potentials in Isolated Ventricular Myocytes

      ,

      Cardiology

      S. Karger AG

      Caffeine, Theophylline, Oscillatory current, Calcium overload, Quinacrine, Acetylcholine

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          Abstract

          The events caused by overdrive-induced calcium overload were studied in guinea pig isolated ventricular myocytes. Overdrive may induce oscillatory potentials (V<sub>os</sub>) and a prolonged depolarization (V<sub>ex</sub>), as well as the underlying currents (I<sub>os</sub> and I<sub>ex</sub>, respectively). Acetylcholine (ACh) reduced or abolished these events, an action which was blocked by atropine. Norepinephrine exaggerated the effects of overdrive, and ACh markedly antagonized such an enhancement. Caffeine at low concentrations increased both I<sub>os</sub> and I<sub>ex </sub>whereas at high concentrations caffeine abolished I<sub>os</sub> but increased I<sub>ex</sub>. Quinacrine abolished both events. Voltage clamp depolarizing steps abolished I<sub>os</sub> (and did not reverse it). Thus, the effects of Ca overload are antagonized by ACh in the absence and presence of sympathetic enhancement. Also, the mechanism underlying I<sub>os</sub> appears to involve an electrogenic Ca extrusion and not an increase in a nonspecific conductance.

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          Author and article information

          Journal
          CRD
          Cardiology
          10.1159/issn.0008-6312
          Cardiology
          S. Karger AG
          0008-6312
          1421-9751
          1991
          1991
          12 November 2008
          : 79
          : 1
          : 20-30
          Affiliations
          Department of Physiology, State University of New York, Health Science Center, Brooklyn, N.Y., USA
          Article
          174853 Cardiology 1991;79:20–30
          10.1159/000174853
          1777911
          © 1991 S. Karger AG, Basel

          Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

          Page count
          Pages: 11
          Categories
          Arrhythmias, Electrophysiology and Electrocardiography

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