3
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Effects of Photoperiod, Absence of Photic Cues, and Suprachiasmatic Nucleus Lesions on Nocturnal Prolactin Surges in Pregnant and Pseudopregnant 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

          The pattern of prolactin (PRL) secretion following mating consists of two daily surges, one nocturnal and the other diurnal. Under a photoperiod of 14L: 10D, the most commonly used lighting regime, the nocturnal PRL surge occurs at about 7 h after the onset of the dark phase. The present study investigated the influence of various photo-periods, constant light and dark and suprachiasmatic nucleus lesion (SCN) on the initiation and expression of the nightly PRL surges. Females were divided into five groups and each group was exposed to a different photoperiod. The five experimental photoperiods were: 22L:2D, 19L:5D, 14L: 10D, 8L:16D and 3L:21D. Following at least 8 weeks of exposure to a photoperiod the females were mated. Multiple daily blood samples for PRL determination (RIA) were obtained via chronic intra-atrial cannulae. In females exposed to a decreased period of darkness the nocturnal PRL surge was advanced with respect to the onset of the dark phase. Conversely, an increase in the length of the dark period to over 10 h/day caused a delay in the appearance of the PRL surge. When the timing of the PRL surge is calculated with respect to the midpoint of the dark or light cycle, it occurs at about the same time under all but the most extreme photoperiod (3L:21D). Prior to the experiments using constant dark or constant light the animals were habituated to the lighting conditions for 4 months. In constant darkness the nocturnal PRL surge was synchronized among all animals and peaked in the early morning; its magnitude and duration were greater than under both constant light and alternating light schedules. In constant light, irregular elevations of PRL were seen throughout the day. No elevation of PRL was found in SCN-lesioned animals following cervical stimulation. The present study demonstrates that the nocturnal PRL surges during pregnancy and pseudopregnancy are entrained to photoperiod, can be shifted within limits under various photoperiods and cannot be initiated following lesions in the SCN. On the basis of this and other studies, it is proposed that the nocturnal PRL surge resembles other endogenous circadian rhythms in the rat, but requires the external stimulation of mating for its occurrence.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1980
          1980
          26 March 2008
          : 31
          : 1
          : 26-33
          Affiliations
          Department of Zoology, George S. Wise Center for Life Sciences, Tel Aviv University, Tel Aviv
          Article
          123046 Neuroendocrinology 1980;31:26–33
          10.1159/000123046
          7393403
          © 1980 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: 8
          Categories
          Original Paper

          Comments

          Comment on this article