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      Effect of Transient Dopamine Antagonism on Thyrotropin-Releasing Hormone-Induced Prolactin Secretion in the Serotonin-Blocked, Estrogen-Treated Ovariectomized Rats

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      ,
      Neuroendocrinology
      S. Karger AG
      Prolactin, Estrogen, Serotonin, Dopamine, Thyrotropin-releasing hormone, Ketanserin

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          Abstract

          Recent studies showed that a brief interruption of dopamine (DA) action markedly increased the thyrotropin-releasing hormone (TRH)-stimulated prolactin (PRL) release. It is thus of interest to delineate whether the estrogen-induced afternoon PRL surge involves the same mechanism. Long-term ovariectomized rats pretreated with polyestradiol phosphate (PEP, 0.1 mg/rat s.c.) for 6 days were used in this study. They also received either P-chlorophenylalanine (PCPA, 250 mg/kg i.p.) or ketanserin (Ket, 10 mg/kg i.p.), two serotonergic drugs known to inhibit the estrogen-induced afternoon PRL surge. Then the animals were either treated with a DA antagonist, domperidone (Domp, 0.01 mg/rat i.v.), or vehicle at 16.00 h on the sampling day. Ten minutes later, the ones receiving Domp were injected with a DA agonist, 2-bromo-α-ergocryptine (CB154, 0.5 mg/rat i.v.), followed 50 min later by the administration of TRH (1 µg/rat i.v.). Plasma samples taken through indwelling intraatrial catheters were assayed for PRL by radioimmunoassay. The estrogen-induced afternoon PRL surges were completely blocked in both PCPA- and Ket-treated animals. A significant PRL surge with similar amplitude, however, was induced by either Domp or TRH, although pretreatment with Domp did not cause any potentiating effect on the action of TRH. On the other hand, Domp induced only a small rise of PRL secretion and TRH was totally ineffective in rats untreated with PEP. It is concluded that both DA antagonism and TRH stimulation can induce significant PRL release in the afternoon of estrogen-treated, serotonin-blocked rats. Our data suggest that the dopaminer-gic tone is intact and functional in animals whose endogenous PRL surges were blocked by serotonergic drugs, while the signal of TRH, or other PRL-releasing factors, may be missing.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1989
          1989
          02 April 2008
          : 49
          : 3
          : 281-285
          Affiliations
          Institute of Physiology, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China
          Article
          125129 Neuroendocrinology 1989;49:281–285
          10.1159/000125129
          2524012
          0df2cfeb-39a2-45df-a56d-e7e1757568b2
          © 1989 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.

          History
          : 08 December 1987
          : 18 July 1988
          Page count
          Pages: 5
          Categories
          Original Paper

          Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
          Serotonin,Prolactin,Ketanserin,Thyrotropin-releasing hormone,Estrogen,Dopamine

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