PT  - JOURNAL ARTICLE
AU  - T Skomedal
AU  - H Aass
AU  - J B Osnes
AU  - N B Fjeld
AU  - G Klingen
AU  - A Langslet
AU  - G Semb
TI  - Demonstration of an alpha adrenoceptor-mediated inotropic effect of norepinephrine in human atria.
DP  - 1985 May 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 441--446
VI  - 233
IP  - 2
4099  - http://jpet.aspetjournals.org/content/233/2/441.short
4100  - http://jpet.aspetjournals.org/content/233/2/441.full
SO  - J Pharmacol Exp Ther1985 May 01; 233
AB  - It has been claimed by other investigators that norepinephrine does not evoke a significant alpha adrenergic inotropic effect in human atria in contrast to epinephrine and phenylephrine, indicating a limitation of a possible functional role of the cardiac alpha adrenoceptors. We therefore characterized the inotropic effects of norepinephrine in isometrically contracting muscle strips from human atria obtained during open heart surgery. Both contraction and relaxation were studied by measuring developed tension and its first and second derivatives. Both the influence of propranolol and prazosin upon the inotropic responses to norepinephrine and the qualitative characteristics of the responses revealed that norepinephrine evoked both alpha and beta adrenergic inotropic effects. The alpha adrenergic response to norepinephrine was qualitatively different from the beta adrenergic effect and qualitatively similar to the alpha adrenergic effect of norepinephrine observed in other mammalian species. Although the alpha adrenergic effect was marked, the beta adrenergic effect was the dominating one as has also been found in other species. It is concluded that also in human atria norepinephrine evokes inotropic effects through both alpha and beta adrenoceptors.