Neuroendocrinology
Original Paper
Twenty-Four-Hour Patterns of Pineal Melatonin and Pituitary and Plasma Prolactin in Male Rats under ‘Natural’ and Artificial Lighting ConditionsLaakso M.-L. · Porkka-Heiskanen T. · Alila A. · Peder M. · Johansson G.Institute of Physiology, University of Helsinki, Finland
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Article / Publication Details
Received: September 29, 1987
Accepted: February 19, 1988
Published online: April 02, 2008
Issue release date: 1988
Number of Print Pages: 6
Number of Figures: 0
Number of Tables: 0
ISSN: 0028-3835 (Print)
eISSN: 1423-0194 (Online)
For additional information: https://www.karger.com/NEN
Abstract
Natural lighting differs from usual artificial lighting mainly as follows: it has larger spectral composition, fluctuations of intensity during the day, higher intensity levels during the night (moonlight, starlight), and gradual changes of illuminance at dawn and dusk. The present experiment was performed in order to study whether these features of lighting affect the 24-hour patterns of melatonin and prolactin in male rats. The rats were kept 7 days in ‘natural’ lighting (sunlight through windows) or in artificial lighting (cool white fluorescent lamps) of similar periodicities (13/1 lh light/ dark). The samples were collected at 3-hour intervals during a 24-hour period. Pineal melatonin contents, pituitary prolactin contents, and plasma prolactin concentrations were measured radioimmunologically. The nocturnal pineal melatonin contents were higher and the daytime contents lower in natural than in artificial lighting conditions. A corresponding ‘strengthening of rhythm’ of prolactin was found in natural lighting. A reason for the higher amplitude variation of melatonin in the natural lighting conditions may be the gradual changes of illuminance at dawn and dusk. The different pituitary and plasma prolactin patterns of the rats kept in the two lighting conditions might partly be explained by a stimulatory effect of melatonin on the production and secretion of prolactin, but other regulatory factors had to be involved, too.
© 1988 S. Karger AG, Basel
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Article / Publication Details
Received: September 29, 1987
Accepted: February 19, 1988
Published online: April 02, 2008
Issue release date: 1988
Number of Print Pages: 6
Number of Figures: 0
Number of Tables: 0
ISSN: 0028-3835 (Print)
eISSN: 1423-0194 (Online)
For additional information: https://www.karger.com/NEN
Copyright / Drug Dosage / Disclaimer
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.
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