The influence of opioid substances on the secretion in vivo and in vitro of corticosterone, corticotrophin (ACTH) and corticotrophin releasing factor (CRF) in the rat was studied. Rats given a single injection of morphine exhibited a marked hypersecretion of ACTH and an exaggeration of the hypothalamo-pituitary-adrenocortical (HPA) response to stress. In contrast, animals rendered tolerant to morphine failed to release ACTH or corticosterone in response either to a subsequent injection of the opiate or to stress. The development of the inhibitory effect paralleled the development of tolerance to the analgesic actions of the drug. The production of ACTH by pituitary segments removed from control animals was not affected by the addition of opioid substances to the incubation medium. However, morphine, met-enkephalin and leu-enkephalin stimulated the secretion of CRF by hypothalami and their effects were competitively antagonized by naloxone. The secretory activity of hypothalami removed from rats treated acutely with morphine was enhanced. In contrast hypothalami from morphine-tolerant rats failed to secrete CRF in response to morphine, met-enkephalin, acetylcholine or 5-hydroxytryptamine. Neither the density nor the affinity of 3H-naloxone binding sites in the hypothalamus was influenced by the morphine treatment. The results suggest the opioid peptides and their receptors play a major role in the regulation of HPA function.

This content is only available via PDF.
Copyright / Drug Dosage / Disclaimer
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.
You do not currently have access to this content.