Functional alpha 1-adrenoceptors in the rat heart during beta-receptor blockade.
In absence of beta-receptor blocking agents, alpha-adrenergic inotropic effects could be demonstrated in the rat myocardium for the synthetic alpha-agonists phenylephrine and methoxamine, but not for the naturally occurring catecholamines, adrenaline and noradrenaline. Other synthetic alpha-agonists were without effects. In the presence of the beta-receptor blocking agent, propranolol or timolol, marked alpha-effects were demonstrated for adrenaline and noradrenaline in both the right and left atria and the right ventricle. The results indicate that alpha-receptors may be functionally important in the beta-blocked myocardium.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004298:Dopamine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000187:drug effects*; D008729:Methoxamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013999:Timolol / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D010656:Phenylephrine; D013999:Timolol; D011433:Propranolol; D008729:Methoxamine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine