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      Contributions of Alpha 1 and Alpha 2-Adrenoceptors to Contractile Response in Canine Blood Vessels

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          Abstract

          Strips of canine saphenous vein, inferior vena cava, and femoral artery were studied isometrically in vitro to compare quantitatively the α<sub>1</sub>- and postsynaptic α<sub>2</sub>-adrenoceptor contributions to the contractile force generated by l-norepinephrine (NE). Effects mediated by each receptor type were measured independently by quantitative blockade of virtually all α<sub>1</sub> -receptors with prazosin, or α<sub>2</sub>-receptors with rauwolscine. Appropriate concentrations of the antagonists were calculated from dissociation constants previously determined by binding or competition with [<sup>3</sup>H]prazosin or [<sup>3</sup>H]rauwolscine in tissue homogenates. The contribution of α<sub>1</sub>-adrenoceptors was larger than that of α<sub>2</sub>-receptors in all vessels. The α<sub>2</sub>-type was responsible for 38% of the maximum unblocked response to NE in saphenous vein, 32% in vena cava, and 28% in femoral artery. The occupation-response relationship for α<sub>1</sub>-receptors was almost linear, without the marked upward convexity reported in some other vessels. α<sub>2</sub>-Occupation-response curves were convex towards the occupation axis, with a relatively small response at low levels of occupation.

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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
          1988
          1988
          23 September 2008
          : 25
          : 4
          : 199-208
          Affiliations
          Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Md., USA
          Article
          158732 Blood Vessels 1988;25:199–208
          10.1159/000158732
          © 1988 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: 10
          Categories
          Research Paper

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