title: The roles of alpha- and beta-adrenoceptors in the chronotropic responses to norepinephrine in carp heart (Cyprinus carpio).
abstract: 1. The chronotropic effect of norepinephrine was studied in isolated spontaneously beating atrial preparations of carp (Cyprinus carpio) heart. 2. Norepinephrine, 0.1 microM, caused a positive chronotropic effect, while at 1 microM it caused either a positive or a negative chronotropic effect. The positive chronotropic effect, observed in 13 preparations, was potentiated by phentolamine and almost completely blocked by propranolol. 3. The negative chronotropic effect observed in the other 5 preparations was greater in the presence of propranolol, reduced by phentolamine and not affected by atropine. 4. These results indicate that alpha- and beta-adrenoceptors may coexist, mediating the negative and positive chronotropic effects, respectively, in isolated atrial preparations of carp heart.
authors.affiliation: Department of Veterinary Pharmacology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Temma
authors.forename: Y
authors.initials: Y
authors.lastname: Komazu
authors.forename: Y
authors.initials: Y
authors.lastname: Shiraki
authors.forename: T
authors.initials: T
authors.lastname: Kitazawa
authors.forename: H
authors.initials: H
authors.lastname: Kondo
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002347:Carps; D003530:Cyprinidae; D004357:Drug Synergism; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*
chemical_list: D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D001285:Atropine; D011433:Propranolol; D009638:Norepinephrine; D010646:Phentolamine