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

      Chronic Posterior Pituitary Lobectomy: Prolonged Elevation of Plasma Prolactin and Interruption of Cyclicity

      ,

      Neuroendocrinology

      S. Karger AG

      Posterior pituitary, Prolactin, Estrous cyclicity

      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

          We previously reported that the posterior pituitary dopaminergic system participates in the inhibition of prolactin (PRL) secretion in both male and lactating female rats. However, posterior pituitary lobectomy (Lobex) of urethane-anesthetized cycling rats resulted in an elevation in plasma PRL for a short time only. This raises a question regarding the importance of input from the posterior pituitary to the control of PRL secretion during the estrous cycle. The objectives of this study were (1) to examine the chronic effects of Lobex on plasma PRL levels in conscious rats and (2) to determine whether the absence of input from the posterior pituitary interferes with estrous cyclicity. Lobex or sham lobectomy were performed under Brevital anesthesia in estrous rats. Blood was collected from a jugular cannula at hourly intervals on the day of surgery and at 09.00, 13.00, and 17.00 h during the following 4 days. Daily water consumption and vaginal cyclicity were monitored for 14 and 20 days, respectively. Within 2 h after Lobex, the plasma PRL levels rose 3- to 4-fold and remained elevated for 3 days before declining to near control levels on the 4th day. None of the Lobex rats resumed cyclicity within 3–4 days, 50% had an interruption of cyclicity for 4–10 days, and the remainder were noncyclic for more than 11 days. Upon resumption of cyclicity, Lobex rats had 11.3 ± 0.4 oviductal ova which is within the normal range for intact ovulating rats. In contrast, 60% of the sham-operated rats resumed cyclicity within 4 days with an afternoon proestrous surge of PRL, whereas 30% became pseudopregnant, as judged by diurnal peaks of plasma PRL levels and a sustained leukocyte smear for 11–13 days. The daily water consumption of Lobex rats was 3-fold higher than that of sham-lobectomized rats for at least 2 weeks. It is concluded that: (1) Lobex results in a prolonged elevation of plasma PRL levels in conscious rats; (2) the eventual decline in plasma PRL is more likely due to a compensatory activation of the hypothalamic dopaminergic system by the Lobex-induced rise in plasma PRL than to a regeneration of the posterior lobe or restoration of its function; (3) the Lobex-induced PRL rise appears to be the cause of interruption of cyclicity, and (4) the data are consistent with the hypothesis that the dopaminergic inhibition of PRL secretion involves two interdependent systems: one consists of the hypothalamus – long portal vessels – and the second comprises of the posterior pituitary -short portal vessels. Depending upon the endocrine conditions and the nature of hormonal or neuronal stimuli, either one or both systems may be activated.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1986
          1986
          01 April 2008
          : 43
          : 4
          : 453-458
          Affiliations
          Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis, Ind., USA
          Article
          124566 Neuroendocrinology 1986;43:453–458
          10.1159/000124566
          3748304
          © 1986 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

          Comments

          Comment on this article