0
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      A D-2 Dopaminergic Agonist Stimulates Secretion of Anterior Pituitary Immunoreactive β-Endorphin in Rats

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Hypothalamic dopamine neurons are known to control circulating levels of immunoreactive β-endorphin (iβ-END) by inhibiting hormone secretion by the intermediate lobe (IL) of the pituitary gland. We examined the ability of the D-2 selective dopaminergic agonist, LY141865, to influence circulating levels of iβ-END in rats and found that in contrast to inhibiting IL secretion, LY141865 increased release of iβ-END from the anterior lobe (AL). Intraperitoneal injection of 1 mg/kg LY141865 transiently increased plasma levels of iβ-END by 7–30 min after drug treatment; plasma prolactin levels were maximally reduced within 15 min and throughout the remaining 2-hour time course of treatment. Doses of 0.3 and 1.0 mg/kg of LY141865 increased circulating iβ-END to 440 and 690%, respectively, of control levels (0.38 ± 0.12 ng/ml, mean ± SEM, n = 6). Lower doses of the D-2 agonist (0.01–0.1 mg/kg) failed to significantly affect plasma iβ-END. Sephadex G-50 chromatography of plasma pools revealed that virtually all of the increase due to LY141865 treatment was immunoreactivity resembling β-lipotropin in molecular size, the principal component of AL secretion of iβ-END. Furthermore, LY141865-evoked release was blocked by pretreatment of rats with dexamethasone (50 µg/kg i.p., 4 h) which inhibits AL but not IL secretion of pro-opiomelanocortin-derived peptides. Stimulation of iβ-END release by LY141865 was also inhibited by the general dopamine antagonist, haloperidol, (0.1–3.0 mg/kg i.p., 2 h) and by the D-2 selective antagonist, sulphide (100 µg/rat i.c.v., 4 h). These results indicate that the effects of LY141865 treatment on pituitary release of iβ-END are mediated by dopaminergic receptor activation, probably of the D-2 type, within the central nervous system. Since neither dopamine nor LY141865 directly influences AL secretion of iβ-END, the effects of D-2 receptor stimulation in vivo are probably mediated by actions of LY141865 on secretion of hypothalamic corticotropin-releasing factor, the principal physiologic stimulator of hormone secretion from pituitary corticotrophs.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1989
          1989
          02 April 2008
          : 50
          : 1
          : 26-32
          Affiliations
          Department of Physiology, Uniformed Services University of the Health Sciences, Bethesda, Md., USA
          Article
          125198 Neuroendocrinology 1989;50:26–32
          10.1159/000125198
          2569171
          © 1989 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: 7
          Categories
          Original Paper

          Comments

          Comment on this article