Acta pharmacologica et toxicologica
-
Acta Pharmacol Toxicol (Copenh) · Jan 1982
Comparative StudyDifferences between alpha-adrenergic and beta-adrenergic inotropic effects in rat heart papillary muscles.
alpha-And beta-adrenergic inotropic effects have been shown to be qualitatively different. In order to further characterize these difference we compared the mechanical response to alpha- and beta-adrenoceptor stimulation, respectively, in electrically driven left ventricular papillary muscles from rat heart. The muscles were stimulated by either isoprenaline (Beta-adrenoceptor stimulation), phenylephrine in the presence of propranolol (alpha-adrenoceptor stimulation) or phenylephrine alone (combined alpha-and Beta-adrenoceptor stimulation). ⋯ Thus Beta-adrenoceptor stimulation activated relaxation compared to contraction by a higher degree than did alpha-adrenoceptor stimulation. This probably reflects different mechanisms of action. While the alpha-effect may rely primarily on an increased calcium influx, the Beta-effect probably is the final result of several subcellular effects of cyclic AMP.