17
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Endogenous Opioid Peptide Regulation of Pulsatile Luteinizing Hormone Secretion during Pregnancy in the Rat

      research-article

      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

          The objective of this study was to determine if endogenous opioid peptides (EOPs) influence the pattern of pulsatile luteinizing hormone (LH) secretion on days 6–8, 14–16 and 22 of gestation in the rat. Unanesthetized animals with two jugular cannulae were initially infused with 0.9% saline during which the control pattern of pulsatile LH release was determined. Possible EOP involvement was then determined by infusion of the EOP receptor antagonist naloxone. Plasma estradiol (E<sub>2</sub>) and progesterone (P) values increased between days 6–8 and 14–16. While plasma E<sub>2</sub> values remained elevated through day 22, plasma P values declined by 90%. As previously reported, mean blood LH levels during the control period on day 22 were higher than on days 6–8 and 14–16 due to an increase in LH pulse frequency. At each stage of gestation naloxone infusion increased mean blood LH levels. This stimulatory action of naloxone was reduced in a dose-dependent fashion by simultaneous infusion with morphine, demonstrating that this effect is mediated via EOP receptors. There was no difference in the in vivo pituitary responsiveness to LH-releasing hormone (LHRH) between rats infused with saline or naloxone at any stage of pregnancy, demonstrating that the stimulatory effect of naloxone was not exerted at the pituitary level. Naloxone increased both the amplitude and frequency of pulsatile LH secretion on days 6–8, and stimulated frequency on days 14–16. The effect on amplitude could not be assessed on days 14–16 because too few rats exhibited pulsatile LH secretion prior to naloxone infusion. The increase in pulse frequency was similar on days 6–8 and 14–16. Although naloxone increased LH pulse amplitude and frequency on day 22, these increases were significantly less than those seen on days 6–8 and 14–16, respectively. Pituitary responsiveness to LHRH was less at all stages of pregnancy in comparison to responsiveness in ovariectomized rats, and progressively declined from days 6–8 through day 22. The lowest responsiveness to LHRH was seen on day 22 and contributed, at least in part, to the diminished increase in LH pulse amplitude in response to naloxone infusion on day 22 compared to days 6–8. The reduced naloxone-induced increment in LH pulse frequency on day 22, occurring coincident with a precipitous decline in plasma P levels, suggests a decreased EOP suppression of pulse frequency at this time. Since recent studies in our laboratory demonstrated that the increase in LH pulse frequency on day 22 is due to loss of the negative feedback action of P on pulsatile LH secretion, we postulate that during pregnancy P suppresses LH pulse frequency through an EOP-mediated mechanism, and as plasma P levels decline on day 22, EOP suppression of pulse frequency is diminished. The result is an increase in LH pulse frequency, and a diminished effect of naloxone on this parameter of pulsatile LH secretion.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1987
          1987
          02 April 2008
          : 46
          : 5
          : 369-378
          Affiliations
          Department of Physiology and Neurobiology, University of Connecticut, Storrs, Conn., USA
          Article
          124847 Neuroendocrinology 1987;46:369–378
          10.1159/000124847
          3323939
          c0fc74c8-9722-4774-9129-aa88058f603b
          © 1987 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.

          History
          : 10 December 1986
          : 29 April 1987
          Page count
          Pages: 10
          Categories
          Original Paper

          Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
          Pulsatile LH release,Opioid peptides,Luteinizing hormone,Progesterone,Pregnancy,Estradiol,Pituitary,LHRH,Naloxone

          Comments

          Comment on this article