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      Vasoactive Intestinal Peptide Inhibits Luteinizing Hormone Secretion: The Inhibition Is Not Mediated by Dopamine

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          Abstract

          Vasoactive intestinal peptide (VIP) is a neuropeptide that is present in the hypothalamus and is probably a neuroen-docrine regulator. The effect of VIP on pulsatile LH secretion in the long-term ovariectomized rat was re-examined in the light of earlier conflicting reports. VIP or saline was infused into the third ventricle at the rat of 15 µl/h and blood was sampled frequently before and during the infusion. VIP at 3.5 nmol/h significantly depressed mean LH levels (p < 0.05) and lowered pulse frequency (p < 0.05), but had no effect on LH pulse amplitude (p > 0.05). VIP at lower levels was not consistently effective, and intraventricular saline was without influence. We examined indirectly whether the site of action of VIP (3.5 nmol/h) was the brain or pituitary by injecting various doses of gonadotropin-releasing hormone (GnRH; 0.5–4.0 ng/100 g BW i.v.) during VlP-induced inhibition of LH secretion and in saline-infused controls. VIP did not alter the response of the pituitary to GnRH or the slope of the GnRH-LH dose-response curve (p > 0.05). We conclude that the inhibitory action of VIP on pulsatile LH secretion is probably exerted in the hypothalamus. To test the hypothesis that dopamine mediates the inhibitory effects of VIP (3.5 nmol/h), animals were pretreated with the dopamine receptor blocking agent pimozide (1.26 mg/kg) in an attempt to block the actions of VIP. Pimozide did not affect the response of LH to VΙP infusion (p > 0.05). We conclude that dopamine is not a likely mediator of the action of VIP.

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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
          : 6
          : 597-603
          Affiliations
          Department of Physiology, University of Western Ontario, London, Ont., Canada
          Article
          125175 Neuroendocrinology 1989;49:597–603
          10.1159/000125175
          2671777
          b224ed1b-74ca-478d-b981-5b98ac575dbd
          © 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
          : 21 July 1988
          : 06 October 1988
          Page count
          Pages: 7
          Categories
          Original Paper

          Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
          Vasoactive intestinal peptide,Pimozide,Pulsatile luteinizing hormone release

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