Stimulation of Myocardial Alpha-Adrenoceptors Mediating Positive Inotropic Effect in Human Atrial Preparations by Adrenaline and Dopamine

  • J. Wagner
  • H. J. Schümann
  • A. Knorr
  • N. Rohm
  • J. Chr. Reidemeister
Conference paper

Abstract

There is no longer any doubt about the presence of α-adrenoceptors in the heart of most mammalian species (10). In contrast to stimulation of ß-adrenoceptors, that of α-adrenoceptors causes a positive inotropic but no chronotropic effect (10). Also in the anaesthetized intact cat, cardiac α-adrenoceptors have been demonstrated, stimulation of which also caused a positive inotropic effect — expressed as increase of left ventricular dp/dtmax — without increase in heart rate (12). The mechanism underlying stimulation of cardiac α-adrenoceptors is different from that of stimulation of ß-adrenoceptors. Whereas stimulation of ß-adrenoceptors is closely related to activation of myocardial adenylate cyclase (9) yielding to an elevation of cyclic AMP, that of α-adrenoceptors is not (2, 6, 7). Moreover, there is evidence that the positive inotropic effect induced by stimulation of α-adrenoceptors is strongly dependent on measures which influence the transsarcolemmal influx of Ca2+ as for instance organic calcium antagonists (3) as well as alteration of the extracellular calcium content or carbachol, for example (11). In isolated rabbit papillary muscle, these α-adrenoceptors have been found to be stimulated by the hormone adrenaline but not by the transmitter noradrenaline (4). This observation already has been obtained in the anaesthetized cat (12).

Keywords

Dopamine Adenosine Phenyl Noradrenaline Adrenaline 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1981

Authors and Affiliations

  • J. Wagner
    • 1
  • H. J. Schümann
    • 1
  • A. Knorr
    • 1
  • N. Rohm
    • 2
  • J. Chr. Reidemeister
    • 2
  1. 1.Pharmakologisches InstitutUniversitätsklinikum EssenEssen 1Germany
  2. 2.Pharmakologisches InstitutAbt. für Thorax- und Kardiovaskuläre ChirurgieEssen 1Germany

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