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Carvedilol blockade of rat myocardial alpha1-adrenoceptors

Eirik Qvigstad1, Jan Bjørn Osnes, Dagny Sandnes

  • 1Department of Pharmacology, University of Oslo, P.O. Box 1057 Blindern, N-0316 Oslo, Norway. eirik.qvigstad@labmed.uio.no

European Journal of Pharmacology
|November 26, 2003
PubMed

Insights

Carvedilol antagonizes myocardial alpha(1)-adrenoceptors, though less potently than beta-adrenoceptors. This alpha(1)-adrenoceptor antagonism may contribute to carvedilol's clinical effects in patients.

Area of Science:

  • Pharmacology
  • Cardiovascular Physiology

Background:

  • Carvedilol is a known alpha(1)- and beta-adrenoceptor antagonist.
  • The specific antagonism of myocardial alpha(1)-adrenoceptors by carvedilol has not been previously studied.

Purpose of the Study:

  • To investigate carvedilol's ability to antagonize functional effects mediated by myocardial alpha(1)-adrenoceptors.
  • To compare its potency in antagonizing alpha(1)- versus beta-adrenoceptors.

Main Methods:

  • Experiments utilized rat papillary muscles in an organ bath.
  • Concentration-response studies assessed inotropic effects of alpha(1)- and beta-adrenoceptor stimulation.
  • Radioligand-binding studies supported functional data.

Main Results:

  • Carvedilol demonstrated antagonism of myocardial alpha(1)-adrenoceptors with an inhibition constant (Ki) of 11.0±3.0 nmol/l.
  • The Ki for beta-adrenoceptor antagonism was 1.2±0.35 nmol/l.
  • Carvedilol was approximately 9-fold less potent against myocardial alpha(1)-adrenoceptors than beta-adrenoceptors.

Conclusions:

  • Carvedilol antagonizes myocardial alpha(1)-adrenoceptors.
  • The potency for alpha(1)-adrenoceptor antagonism is lower compared to beta-adrenoceptors.
  • This alpha(1)-adrenoceptor antagonism may play a role in carvedilol's clinical efficacy.

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