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      Serotonin and Dopamine Independently Regulate Pituitary β-Endorphin Release in vivo

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          Abstract

          Serotonin and dopamine neurons have been shown to exert a stimulatory and inhibitory control, respectively, over pituitary release of β-endorphin-like immunoreactivity (β-END-LI). In the present study we sought to determine whether an interaction exists between these two reciprocal mechanisms regulating β-END-LI in the rat. The intraperitoneal (i.p.) administration of 5 mg/kg quipazine, a serotonin receptor agonist, or 2.5 mg/kg haloperidol, a dopamine receptor antagonist, each elevated circulating levels of β-END-LI 5-fold over control levels by 30 min post-injection. Pretreatment (1 h) with 5 mg/kg, i.p., cinanserin, a serotonin receptor antagonist, completely blocked the quipazine-induced rise in β-END-LI without affecting the elevated levels of β-END-LI in haloperidol-treated animals. Conversely, pretreatment (2 h) with 1 mg/kg, i.p., bromocriptine, a dopamine receptor agonist, had no effect on quipazine-induced release of β-END-LI but did completely prevent the rise in plasma β-END-LI due to haloperidol treatment. Gel filtration chromatography revealed that quipazine and haloperidol treatments elevated plasma levels of both β-END-size immunoreactivity and β-lipotropin (β-LPH)-sized immunoreactivity though to different relative degrees. However, since circulating levels of β-LPH serve as a marker for anterior lobe (AL) β-END-LI secretion, serotonin and dopamine appear to exert stimulatory and inhibitory control, respectively, over AL β-END-LI release. Further, the quipazine-induced rise in total plasma β-END-LI primarily resembled β-LPH in size and was blocked by cinanserin but not bromocriptine pretreatment. And conversely, bromocriptine but not cinanserin prevented the haloperidol-induced rise in circulating β-END-LI. In comparison to quipazine, haloperidol had a considerably more marked effect on plasma levels of β-END-sized immunoreactivity. Together, these findings support the conclusion that dopamine and serotonin neurons exert reciprocal and independent control over pituitary β-END-LI secretion in vivo.

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          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
          : 42
          : 3
          : 191-196
          Affiliations
          Department of Physiology, Uniformed Services University of the Health Sciences, Bethesda, Md., USA
          Article
          124439 Neuroendocrinology 1986;42:191–196
          10.1159/000124439
          3005900
          © 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: 6
          Categories
          Original Paper

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