Beta 2-adrenoceptor-mediated positive dromotropic effects on atrioventricular node of dogs.
The functional significance of beta 2-adrenoceptors in atrioventricular (AV) nodal conduction was investigated by using canine isolated blood-perfused AV node preparations. Dose-dependent shortening of the atrio-His bundle (A-H) interval by dl-procaterol hydrochloride hemihydrate (0.03-1 nmol) injected intra-arterially into the AV node artery was affected little by an infusion of dl-atenolol (10 nmol/min) into the same artery, whereas the dose-response curve for the positive dromotropic effect of procaterol was shifted markedly to the right by approximately 1.5 and 2.5 log units with ICI 118551 [erythro-dl-1-(7-methylindan-4-yloxy)-3-isopropylamino-bu tan-2-ol]- hydrochloride (1 and 10 nmol/min). The positive dromotropic effect of dl-T-1583 [alpha-(3,4,5-trimethoxyphenethylaminomethyl)-3,4-dihydroxybenzyl- alcohol] hydrochloride (30-300 pmol), a selective beta 1-adrenoceptor agonist, was shifted to the right by approximately 1.2 log units with dl-atenolol (10 nmol/min) but was affected little by ICI 118551 (10 nmol/min). The dose-response curve for l-isoproterenol hydrochloride (3-100 pmol) was shifted to the right by 0.7 log unit with ICI 118551 (10 nmol/min) and by 1.7 log units with atenolol (10 nmol/min). The dose-response curve for dl-norepinephrine (0.03-1 nmol) was shifted to the right by 1.0 log unit with atenolol only, whereas the curve for l-epinephrine (0.03-1 nmol) was shifted by 0.45 log unit with ICI 118551 (10 nmol/min). These results suggest that both beta 1- and beta 2-adrenoceptors, which coexist on the AV node, play a functional role in AV nodal conduction.
Department of Pharmacology, Yamanashi Medical College, Japan.
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Motomura
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Hashimoto
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001283:Atrioventricular Node / Q000187:drug effects / Q000502:physiology*; D002395:Catecholamines / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D006329:Heart Conduction System / Q000502:physiology; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology*; D017265:Procaterol; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D004983:Ethanolamines; D011943:Receptors, Adrenergic, beta; C059333:T 1583; D007545:Isoproterenol; D017265:Procaterol