0
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Hyperresponsiveness to the Inhibitory Action of Dopamine Agonists on Luteinizing Hormone Secretion in the Monosodium-L-Glutamate-Treated, Orchidectomized Rat

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          The tuberoinfundibular (A12) dopaminergic pathway, which originates in the arcuate and periventricular nuclei, is thought to play an inhibitory role in the regulation of episodic luteinizing hormone (LH) secretion. Neonatal treatment of rats with the neurotoxin monosodium-L-glutamate (MSG) causes extensive damage to the arcuate nuclei and up to 60% depletion of dopamine (DA) in the mediobasal hypothalamus. We hypothesized that such DA depletion should result in a hyperresponsiveness to subsequent administration of a DA agonist. To test this hypothesis, male rats were treated neonatally with MSG. Control rats received injections of equiosmotic saline. As adults the rats were orchidectomized and fitted with indwelling venous catheters. Blood samples were taken from these unanesthetized, unrestrained rats at 5-min intervals for a 1-hour period, at which time the animals received an intraperitoneal injection of one of the following drugs: apomorphine (0.8 mg/kg, a DA receptor agonist), bromocriptine (8.0 mg/kg, a DA receptor agonist), 0.9% saline (vehicle for apomorphine) or 95% ethanol (vehicle for bromocriptine). Blood sampling was continued for a further 2–2.5 h. Plasma LH was measured by RIA. Both apomorphine and bromocriptine produced striking inhibition of circulating LH levels in MSG-treated rats. Neither of the control treatments altered pulsatile LH secretion patterns. Administration of exogenous gonadotropin-releasing hormone produced LH peaks in all animals so treated, including those whose endogenous LH secretion had been inhibited by the DA agonists. These findings suggest that the depletion of DA induced by neonatal MSG treatment results in a supersensitivity to DA agonists. Furthermore, they support the theory that tuberoinfundibular DA is an inhibitory regulator of episodic LH secretion in the castrate rat, and that this inhibitory effect occurs at a suprapituitary site.

          Related collections

          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1986
          1986
          01 April 2008
          : 44
          : 1
          : 95-101
          Affiliations
          Department of Physiology, University of Western Ontario, London, Ontario, Canada
          Article
          124628 Neuroendocrinology 1986;44:95–101
          10.1159/000124628
          3024058
          © 1986 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
          Original Paper

          Comments

          Comment on this article