Effects of Brain Antiestrogen Implants on Maternal Behavior and on Postpartum Estrus in Pregnant Rats

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Abstract

To test the hypothesis that the onset of maternal behavior is stimulated by estrogen, we examined the effects of medial preoptic area (MPOA) or ventromedial hypothalamus (VMH) implants of the antiestrogen 4-hydroxytamoxifen (OH-TAM) on pre- and postpartum maternal behavior and on postpartum estrus in rats. On day 20 of pregnancy, animals were implanted bilaterally with OH-TAM or cholesterol cannulae into MPOA or VMH. Unilateral cannulae of OH-TAM were also placed into MPOA. Females were tested with newborn pups for the onset of immediate retrieval, prepartum, at noon on day 21, at midnight of the day 21, and 1 day following parturition (which occurred on day 22). On the evening of parturition, implanted animals were tested with stimulus males for the occurrence of postpartum estrus. In order to examine the influence of estrogen on maternal behavior in the absence of parturitional experience, antiestrogen-implanted animals were delivered surgically (cesarean section) and were observed for the display of maternal behavior at various times after surgery. At noon of day 21, only a few animals in any group retrieved pups. However, 12 h later, females that received bilateral OH-TAM implants into MPOA remained nonresponsive, while over 80% animals in other groups retrieved and gathered pups. The antiestrogen did not disrupt the display of postpartum maternal behavior in those females that were allowed to undergo normal parturition, but it significantly reduced the number of cesarean-delivered animals showing maternal behavior. Bilaterial implants of OH-TAM into VMH, but not into MPOA, effectively blocked postpartum estrus. The MPOA implants of OH-TAM resulted in a significant reduction in cytoplasmic estrogen receptor levels and an increase in nuclear estrogen receptor concentrations. The results of these experiments lend support to the current hypothesis that estrogen acts most effectively in the MPOA to stimulate maternal behavior and in the VMH to facilitate sexual receptivity.

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Journal

Journal ID (publisher-id): NEN

Journal ID (nlm-ta): Neuroendocrinology

Journal ID (doi): 10.1159/issn.0028-3835

Title: Neuroendocrinology

Publisher: S. Karger AG

ISSN (Print): 0028-3835

ISSN (Electronic): 1423-0194

Publication date Subscription-year: 1987

Publication date (Print): 1987

Publication date (Electronic): 02 April 2008

Volume: 46

Issue: 6

Pages: 522-531

Affiliations

Institute of Animal Behavior, Rutgers-The State University of New Jersey, Newark, N.J., USA

Article

Publisher ID: 124875 Other ID: Neuroendocrinology 1987;46:522–531

DOI: 10.1159/000124875

PubMed ID: 3696383

SO-VID: be571256-45a6-4694-993a-a5a62a9f6622

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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

Date received : 19 December 1986

Date accepted : 30 June 1987

Page count

Pages: 10

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