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      Photoperiod Affects the Gonadotropin- Releasing Hormone Neuronal System of Male Prairie Voles <bolditalic>(Microtus ochrogaster)</bolditalic>

      ,

      Neuroendocrinology

      S. Karger AG

      Photoperiod, Vole, Rhythm, Gonadal steroids, Gonadotropin-releasing hormone

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          Abstract

          In order to maximize survival, animals inhabiting temperate and boreal latitudes exhibit numerous adaptations to changing seasons. Central among this suite of coping strategies is the cessation of breeding during the suboptimal conditions of winter. Many nontropical rodents inhibit reproduction well in advance of winter in response to short day lengths. Male prairie voles (Microtus ochrogaster) are small temperate-zone rodents that vary in their reproductive response to photoperiod. Some male voles undergo complete gonadal regression during short days (responders) while others fail to inhibit reproduction when exposed to short day lengths (nonresponders). The neuroendocrine mechanisms regulating this differential response to photoperiod have not been investigated in this species. Presumably, photoperiod can act at any or all levels of the hypothalamo-pituitary-gonadal (HPG) axis to regulate reproduction. The present study sought to determine the contribution of the GnRH system to this variable reproductive response to photoperiod. Male prairie voles were housed in either long or short day lengths for 10 weeks. As shown with immunohistochemistry, voles that underwent gonadal regression in response to short photoperiods exhibited increased GnRH neuron numbers in the preoptic area/anterior hypothalamus (POA/AH) relative to both long-day animals and short-day voles that maintained reproductive function. Mean optical density of staining and cell size did not differ among groups. These data suggest that the differential reproductive response to photoperiod in male voles is mediated, in part, by alterations in the GnRH neuronal system.

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          Most cited references 1

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          Photoperiod-Nonresponsive Morphs: A Possible Variable in Microtine Population-Density Fluctuations

           Randy Nelson (1987)
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            Author and article information

            Journal
            NEN
            Neuroendocrinology
            10.1159/issn.0028-3835
            Neuroendocrinology
            S. Karger AG
            0028-3835
            1423-0194
            1999
            April 1999
            21 April 1999
            : 69
            : 4
            : 238-244
            Affiliations
            Behavioral Neuroendocrinology Group, Departments of Psychology, Neuroscience, and Division of Reproductive Biology, The Johns Hopkins University, Baltimore, Md., USA
            Article
            54424 Neuroendocrinology 1999;69:238–244
            10.1159/000054424
            10207275
            © 1999 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
            Figures: 4, Tables: 2, References: 33, Pages: 7
            Categories
            Reproductive Neuroendocrinology

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