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      Effect of Intraventricular β-Endorphin and Morphine on Hypothalamic-Pituitary-Adrenal Activity and the Release of Pituitary β-Endorphin

      , , ,

      Neuroendocrinology

      S. Karger AG

      Pituitary release, β-Endorphin, ACTH, Corticosterone

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          Abstract

          The effects of intraventricular (i.v.t.) morphine sulfate (MS) and β-endorphin (β-EP) on pituitary-adrenal activity and the release of pituitary β-EP were studied in rats. Pituitary-adrenal activity was monitored by measuring plasma corticosterone (CS) levels. 45 min after i.v.t. injection, both MS and β-EP caused dose-related increases in plasma CS, with β-EP being approximately ten times more potent on a molar basis. MS injected i.v.t. at 0.3, 1.0, 3.0 and 10.0 μg did not cause a significant reduction in pituitary immunoreactive (i.r.) β-EP, but did cause an increase in plasma i.r. β-EP at 3 μg of MS. β-EP injected i.v.t. at 1.5 μg caused a reduction of pituitary i.r. β-EP. Since i.v.t.-injected β-EP may have contributed to the measured plasma i.r. β-EP, a nonimmunoreactive analog (Des-Asn<sup>20</sup>-β<sub>c</sub>-EP) was used to assess the change in plasma i.r. β-EP. 5 μg of Des-Asn<sup>20</sup>-β<sub>c</sub>-EP injected i.v.t. caused increases in plasma i.r. β-EP and CS, as well as a 40% reduction in pituitary i.r. β-EP. The concomitant intraperitoneal (i.p.) injection of naloxone HC1 (10 mg/kg) significantly blocked the increase in plasma CS induced by 5 μg of β-EP. When naloxone HC1, 10 mg/kg was injected alone, a significant increase in plasma CS was found. The results indicate that i.v.t. β-EP is more potent than MS in causing the release of pituitary ACTH and β-EP. These findings are consistent with a role for brain endorphins in the regulation of CRF release.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1981
          1981
          26 March 2008
          : 33
          : 3
          : 170-175
          Affiliations
          Department of Pharmacology and Toxicology, The Medical College of Wisconsin, Milwaukee, and Veterans Administration Hospital, Wood, Wisc, USA
          Article
          123224 Neuroendocrinology 1981;33:170–175
          10.1159/000123224
          6270585
          © 1981 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: 6
          Categories
          Original Paper

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