In addition to its traditional role as a circulating vasoactive peptide, vasopressin (VP) has been shown to play significant roles in central cardiovascular processing. The recent description of VP receptors within the subfomical organ (SFO) has suggested this circumventricular organ (CVO) as a potential locus for feedback actions of circulating VP on the brain. The well-established anatomical connections between SFO and hypothalamic autonomic control centers provide further arguments in support of such a view. This study was undertaken to determine the physiological consequences of activation of VP receptors within the SFO of urethane anesthetized rats. Micro injection (0.5 µl) of 5 pmol VP into SFO resulted in significant decreases in blood pressure (BP, mean AUC-638.3 ± 110.3 mm Hg·s, p < 0.01, n = 13) without a change in heart rate (HR, mean AUC 7.9 ± 14.0 beats, p > 0.05, n = 12), effects which were repeatable. These depressor effects were specific to microinjection locations within this CVO as similar VP microinjections into non-SFO tissue were without effect on BP (mean AUC 245.4 ± 111.5 mm Hg·s, p > 0.05, n = 10), or HR (mean AUC 1.8 ± 3.1 beats, p > 0.05, n = 9). In contrast to the former depressor effects, VP microinjection (5 pmol in 0.5 µl) into the third ventricle produced large increases in BP (mean AUC 1,461.8 ± 368.97 mm Hg·s, p < 0.05, n = 6) again with no change in HR (mean AUC 1.4 ± 5.96 beats, p > 0.05, n = 6). The hypotensive effects observed in response to VP microinjection into SFO were abolished by systemic treatment with a V1 receptor antagonist (mean AUC 89.5 ± 67.7 mm Hg·s, p > 0.05) compared to BP response before V1 receptor blockade (mean AUC -605.9 ± 119.8 mm Hg·s, n = 4). These results suggest that the SFO may be an essential structure in the feedback control loop through which circulating VP influences descending autonomic pathways involved in cardiovascular control.

Keywords:
Vasopressin, Vasopressin receptors, Subfornical organ, Blood pressure
This content is only available via PDF.
© 1997 S. Karger AG, Basel
1997
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.