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      Role of Nitric Oxide and Potassium Channels in the Cholinergic Relaxation of Rabbit Ear and Femoral Arteries: Effects of Cooling

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          Abstract

          The main objective of this work was to study the role of potassium channels in the cholinergic relaxation of cutaneous arteries during cooling. Acetylcholine (10<sup>–8</sup>–10<sup>–4</sup> M) produced isometric concentration-dependent relaxation of precontracted segments of rabbit ear (cutaneous) and femoral (noncutaneous) arteries; this relaxation was higher at 24 ° C (cooling) than at 37 °C in ear, but not in femoral, arteries. In both types of arteries, at 37 and 24 °C, the relaxation to acetylcholine was partially reduced by the inhibitor of nitric oxide synthase N<sup>G</sup>-nitro- L-arginine methyl ester ( L-NAME, 10<sup>–4</sup> M), and the relaxation that remained after L-NAME was higher at 24°C than at 37°C in ear, but not in femoral, arteries. At 37 and 24°C, the persistent relaxation to acetylcholine after L-NAME was further reduced by smooth muscle depolarization with medium containing a high concentration of potassium (6 × 10<sup>–2</sup> M), and with the nonspecific inhibitors of potassium channels tetraethylammonium (10<sup>–2</sup> M) or 4-aminopyridine (5 × 10<sup>–3</sup> M) in both ear and femoral arteries. In ear arteries, the inhibitor of high conductance calcium-activated potassium channels charybdotoxin (10<sup>–7</sup> M), alone or combined with L-NAME, reduced the relaxation to acetylcholine at 24°C, but not at 37°C. In femoral arteries, charybdotoxin alone did not modify, but combined with L-NAME reduced, the relaxation to acetylcholine at either temperature. At 37 and 24 °C, the inhibitor of low conductance calcium-activated potassium channels apamin (10<sup>–7</sup> M), the inhibitor of ATP-dependent potassium channels glibenclamide (10<sup>–5</sup> M) and the cyclooxygenase inhibitor meclofenamate (10<sup>-5</sup> M), alone or combined with L-NAME, did not modify the relaxation of both ear and femoral arteries to acetylcholine. These results suggest: (1) the cholinergic relaxation of cutaneous (ear) and noncutaneous (femoral) arteries could be mediated by endothelial nitric oxide and by activation of potassium channels, and (2) cooling increases the relaxation of cutaneous arteries to cholinergic stimulation, which may be mediated, in part, by an increased response of potassium channels.

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          Author and article information

          Journal
          JVR
          J Vasc Res
          10.1159/issn.1018-1172
          Journal of Vascular Research
          S. Karger AG
          1018-1172
          1423-0135
          1995
          1995
          24 September 2008
          : 32
          : 6
          : 387-397
          Affiliations
          Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma, Madrid, España
          Article
          159114 J Vasc Res 1995;32:387–397
          10.1159/000159114
          8562811
          © 1995 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
          Research Paper

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