Physiologically Significant Inhibitory Hypothalamic Action of Substance P on Prolactin Release in the Male Rat

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Abstract

To evaluate a possible physiological role of endogenous substance P (SP) in the control of prolactin (PRL) release, conscious adult male rats were given injections of a specific antiserum against SP (anti-SP) into the third ventricle (3 µl) or intravenously (0.5 ml). Third-ventricular injection of anti-SP induced a significant increase in plasma PRL levels when compared to values in control animals injected with normal rabbit serum (p < 0.02). Plasma PRL concentrations were significantly elevated within 2 h after injection of antiserum and remained elevated for the 4-hour duration of the experiment. In contrast, injections of large doses of anti-SP intravenously had no effect on plasma PRL levels. In order to confirm the effect of SP itself, synthetic SP was injected intravenously and intraventricularly. Opposite effects of SP on PRL release were observed after intravenous and intraventricular injections of low or high doses of the peptide. A lower dose of SP (10 ng, 7.42 pmol) injected into the third ventricle suppressed the release of PRL (p < 0.01), whereas higher doses (1 µg, 0.74 nmol, or 5 µg, 3.71 nmol) had a stimulatory effect on PRL release (p < 0.01). Similarly, a low dose of SP (0.1 µg, 0.07 nmol) injected intravenously lowered plasma PRL (p < 0.05). Large doses of intravenous SP (50 µg, 37.1 nmol) dramatically stimulated PRL release (p < 0.001). To evaluate a possible direct action of SP on PRL release from the anterior pituitary, the peptide was incubated with dispersed anterior pituitary cells for 1 h. The release of PRL from incubated anterior pituitary cells was not affected at any dose of synthetic SP tested (10<sup>–9</sup>–10<sup>–6</sup> M. These data indicate that in the male rat endogenous SP is a physiologically significant inhibitor of basal release of PRL, via a hypothalamic action, although higher, presumably pharmacological doses of SP stimulate the release of this hormone also via hypothalamic action.

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Journal

Journal ID (publisher-id): NEN

Journal ID (nlm-ta): Neuroendocrinology

Journal ID (doi): 10.1159/issn.0028-3835

Title: Neuroendocrinology

Publisher: S. Karger AG

ISSN (Print): 0028-3835

ISSN (Electronic): 1423-0194

Publication date Subscription-year: 1990

Publication date (Print): 1990

Publication date (Electronic): 03 April 2008

Volume: 52

Issue: 1

Pages: 22-27

Affiliations

^aDepartment of Obstetrics and Gynecology, Tachikawa Kyosai Hospital, Tokyo, Japan; ^bDepartment of Obsterics and Gynecology, University of Iowa College of Medicine, Iowa, Cita, Iowa; ^cNeuropeptide Division, Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, Tex.; ^dBioproducts Department, The Dow Chemical Company, Midland, Mich.; ^eDepartment of Anatomy, The Ohio State University, Columbus, Ohio, USA

Article

Publisher ID: 125533 Other ID: Neuroendocrinology 1990;52:22–27

DOI: 10.1159/000125533

PubMed ID: 1697659

SO-VID: 36eef14c-d765-44db-bf5a-13136dff9057

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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

Date received : 29 March 1989

Date accepted : 16 January 1990

Page count

Pages: 6

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