α-adrenergic regulation of action potentials in isolated rat cardiomyocytes

Stephen M. Vogel, Andre Terzic

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Radioligand binding studies and studies in which inositol phosphate levels were assayed have provided substancial evidence for the existence of α1-adrenoceptors in isolated rat ventricular myocytes, a pure cardiac preparation free of neuronal and vascular elements. Since correlational electrophysiological studies have not been carried out in this model, we investigated α-adrenergic effects on action potentials using intracellular microelectrodes to impale the myocytes. Epinephrine, in the presence of propranolol (10-6 M), rapidly increased the action potential duration in a concentration-dependent manner (threshold concentration of 30 nM, EC50 of 100 nM). The maximal upstroke velocity and overshoot of Ca2+-mediated action potentials (15 mM K+) were also incresed. Epinephrine did not significantly affect the resting membrane potential. The α1-adrenoceptor antagonist, prazosin (10-7 M) blocked epinephrine's effects. LiCl (10 mM), an inhibitor of inositol-phosphate phosphates potentiated the effects of epinephine (30 nM). The results suggest that the isolated rat cardiomyocyte is a suitable preparation for examining the ionic and molecular mechanisms of direct α-adrenergic effects on the cardiac membrane.

Original languageEnglish (US)
Pages (from-to)231-239
Number of pages9
JournalEuropean Journal of Pharmacology
Volume164
Issue number2
DOIs
StatePublished - May 19 1989

Keywords

  • Cardiac action potential
  • Epinephrine
  • Prazosin
  • α-Adrenoceptors
  • β-Adrenoceptor blockade

ASJC Scopus subject areas

  • Pharmacology

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