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      Effect of Atropine on Vascular Adrenergic Neuroeffector Transmission

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          Abstract

          Atropine, homatropine, scopolamine, procaine, lidocaine and phentolamine inhibited the contractile response of rabbit isolated pulmonary artery elicited by electrical-field stimulation. Methylatropine had no effect. The inhibition induced by atropine (2 × 10<sup>–6</sup>–2 × 10<sup>–4</sup> m) had a rapid onset of action and then remained almost constant. The inhibition was slowly reversible. The potency of atropine as an inhibitor of responses to field stimulation was very much less than the potency of phentolamine. The inhibition was not antagonized by cocaine or (+)-amphetamine. Atropine (3 × 10<sup>–5</sup> and 3 × 10<sup>–4</sup> m) enhanced the electrical-field-stimulation-induced outflow of tritium from the pulmonary artery preloaded with <sup>3</sup>H-(–)-noradrenaline. In contrast, atropine in a concentration-dependent manner either had no effect or slightly decreased the tyramine-induced outflow of tritium. Atropine reduced the contractile response of the pulmonary artery evoked by tyramine. Atropine (10<sup>–4</sup> and 3 × 10<sup>–4</sup> m) and phentolamine inhibited the arterial contractions elicited by exogenous (–)-noradrenaline in an apparently competitive manner. The contractions of rabbit isolated aorta elicited by (–)-noradrenaline, serotonin and histamine were inhibited by atropine (10<sup>–5</sup> and 10<sup>–4</sup> m). Atropine was very much less potent in antagonizing noradrenaline, histamine and serotonin than in antagonizing acetylcholine. The inhibitory potency of atropine, procaine and lidocaine on the accumulation of <sup>3</sup>H-(–)-noradrenaline by rabbit aorta in vitro was much less than that of cocaine. The relationship between the aortic concentration of <sup>3</sup>H-atropine and in vitro accumulation was almost linear. The accumulation was slightly higher at37 °C than at 1 °C. The results suggest that atropine blocks α-adrenoceptors, both presynaptically at the adrenergic neurone terminals and postsynaptically at the smooth muscle. In addition, atropine may possibly act in a nonspecific manner at postsynaptic sites.

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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
          1977
          1977
          18 September 2008
          : 14
          : 6
          : 325-347
          Affiliations
          Department of Pharmacology, University of Odense, Odense
          Article
          158141 Blood Vessels 1977;14:325–347
          10.1159/000158141
          © 1977 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: 23
          Categories
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