The purpose of the present study was to determine if the calcium channel activator, Bay K 8644, enhances the vasoconstrictor actions of selective α1- and α2-adrenoceptor agonists in canine saphenous vein. Phenylephrine (PE) and St 587 were used as fully and partially selective α1-adrenoceptor agonists, B-HT 920 and B-HT 958 were used as fully and partially selective α1-adrenoceptor agonists. Bay K 8644 (10–8M) markedly potentiated B-HT-958-mediated vasoconstrictor responses with a leftward shift and an increase in the maximum response of the logarithmic dose-response curve. Bay K 8644 produced less potentiation of responses to B-HT 920 and had minimal effects on responses to St 587 and PE. The intrinsic activities of the α-adrenoceptor agonists, as compared to the maximum response obtained by norepinephrine, in decreasing order, were PE > St 587 > B-HT 920 > B-HT 958, whereas the susceptibility of α-adrenoceptor agonists to potentiation by Bay K 8644 in decreasing order were B-HT 958 > B-HT 920 > St 587 > PE. These results suggest that Bay K 8644 preferentially improves the receptor-response coupling of α-adrenoceptor agonists with low intrinsic activity (α2-agonists) versus agonists with high intrinsic activity (α1-agonists) in canine saphenous vein.

Keywords:
Canine saphenous vein, Alpha-adrenoceptors, Calcium channel activator, Intrinsic activity, Full agonist, Partial agonist
This content is only available via PDF.
© 1987 S. Karger AG, Basel
1987
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.