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      Species Differences in Behavioral and Neural Sensitivity to Estrogen in Whiptail Lizards: Correlation with Hormone Receptor Messenger Ribonucleic Acid Expression

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          Abstract

          Cnemidophorus uniparens is a unisexual species of whiptail lizard of hybrid origin whereas C. inornatus is a sexual species and the maternal ancestor of C. uniparens. Together they represent an excellent model system for investigating the evolution of hormone-brain-behavior relationships. Normal circulating estradiol (E) concentrations in C. uniparens are approximately 5-fold lower than those of female C. inornatus in a similar reproductive state. Experiments were performed to determine whether (i) C. uniparens is more sensitive to E, and (ii) whether the difference in sensitivity is correlated with differences in estrogen receptor (ER)-mRNA expression in the brain. Dose-response curves reveal that ovariectomized C. uniparens are more responsive than ovariectomized C. inornatus to exogenous estradiol 17β-benzoate (EB). EB is more effective in C. uniparens at inducing receptive behavior and progesterone receptor (PR) gene expression in the ventromedial nucleus of the hypo-thalamus (VMH). In situ hybridization analysis of ER-mRNA expression revealed no species differences in ER-mRNA content in the VMH of ovariectomized animals. Treatment of ovariectomized animals with EB resulted in a greater induction of ER-mRNA expression in the VMH of C. uniparens compared to C. inornatus. These results indicate that the differences in behavioral sensitivity to E lie in the estrogen target neurons in the brain region controlling receptive behavior, the VMH, and that the difference in sensitivity cannot be explained by species differences in the basal rate of ER gene expression.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1995
          1995
          09 April 2008
          : 61
          : 6
          : 680-686
          Affiliations
          Department of Zoology, University of Texas at Austin, Tex., USA
          Article
          126895 Neuroendocrinology 1995;61:680–686
          10.1159/000126895
          7659192
          © 1995 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: 7
          Categories
          Gonadotropins and Reproduction

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