[Chronotropic effects of alpha-agonist on the rat isolated right atria].
This study was performed to investigate whether or not alpha-adrenergic stimulation exerts a chronotropic effect on the heart. Isolated right atria of rats were used. Phenylephrine (10(-5)-10(-4) mol/l), an alpha-agonist, did not affect the rate of the atrial beat under treatment with propranolol (1 x 10(-6) mol/l), a beta-blocker. When the atrial rate was increased to approximately double by treatment with isoproterenol (1 x 10(-8) mol/l) or forskolin (1 x 10(-6) mol/l), phenylephrine at the same doses significantly reduced the rate by about 6%. This effect was blocked by phentolamine (1 x 10(-6) mol/l). These results suggest that alpha-adrenoceptors function to reduce heart rate in the atria, of which rate is raised through intracellular cAMP activity.
Nakano
K
K
Department of Pharmacoloy, Nippon Medical School, Japan.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D003864:Depression, Chemical; D006325:Heart Atria / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011942:Receptors, Adrenergic, alpha; D005576:Colforsin; D010656:Phenylephrine; D007545:Isoproterenol