Diurnal Fluctuations in Methionine-Enkephalin Levels in the Hypothalamus and Preoptic Area of the Male Rat: Effects of Pinealectomy

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Abstract

Methionine-enkephalin (met-enk) levels were measured at 09.30–10.30, 16.30–17.30 and 23.30–00.30 h in the anterior hypothalamus-preoptic area (AHPOA), medial basal hypothalamus (MBH), anterior, intermediate and posterior lobe of the pituitary gland of male rats. Met-enk levels in the AHPOA and MBH fluctuated significantly through a 24-hour period; from low levels at 09.30–10.30 h, met-enk in the AHPOA and MBH rose slowly in the afternoon to reach peak concentrations at 23.30–00.30 h. Pinealectomy appears to depress or shift the normally occurring increments in met-enk levels at 23.30–00.30 h in the AHPOA only. Serum testosterone (T) levels displayed an inverse relationship with the met-enk rhythm; high concentrations during the day were associated with low met-enk levels and as T levels decreased to a nadir at 23.30–00.30 h, the met-enk in the MBH and AHPOA attained peak concentrations. Daily changes in serum T levels were not affected by pinealectomy.

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Author and article information

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: 1982

Publication date (Print): 1982

Publication date (Electronic): 26 March 2008

Volume: 35

Issue: 1

Pages: 28-31

Affiliations

^aDepartments of Metabolism and Reproduction, College of Veterinary Medicine, ^bDepartment of Animal Sciences, ^cDepartment of Obstetrics and Gynecology, College of Medicine, University of Florida, Gainesville, Fla., USA

Article

Publisher ID: 123350 Other ID: Neuroendocrinology 1982;35:28–31

DOI: 10.1159/000123350

PubMed ID: 7202129

SO-VID: fbd57dd0-d740-40fd-af29-7e36408bbe55

License:

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 : 06 November 1981

Date accepted : 07 January 1982

Page count

Pages: 4

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