Effects of some catecholamines on the cat cardiovascular system: interactions with adrenoceptor antagonists.
The effects of intravenous infusions of norepinephrine, epinephrine, isoproterenol, N-t-butylnorepinephrine, oxymethyleneisoproterenol, and RO363 on heart rate, mean arterial blood pressure, cardiac output, total peripheral resistance, and stroke volume were evaluated in chloralose-anaesthetized cats before and after phentolamine, propranolol, atenolol, and butoxamine. Pressor responses to both norepinephrine and epinephrine largely resulted from alpha-receptor-mediated increases in total peripheral resistance. Vasomotor reversal was noted with both drugs in the presence of alpha-receptor blockade. Dilator responses to norepinephrine were abolished by the beta 1-receptor selective antagonist atenolol, as were those to the beta 1-receptor selective agonists oxymethyleneisoproterenol and RO363. Dilator responses to epinephrine were abolished by the beta 2-receptor selective antagonist butoxamine, as were those to N-t-butylnorepinephrine (beta 2-selective) and isoproterenol (nonselective). These results indicate that in addition to beta 2-receptors, beta 1-receptors subserving vasodilatation occur in the cat vasculature. Atenolol displayed agonist-dependent inhibition of the cardiac responses. Responses to noradrenaline, RO363, and oxymethyleneisoproterenol were blocked to a greater extent than were those to epinephrine, N-t-butylnorepinephrine, and isoproterenol. Butoxamine did not display any marked agonist-dependent inhibition of cardiac responses. Nevertheless, the results are in accord with previous suggestions that cardiostimulant beta 2-receptors exist in the cat heart. Interpretation of the actions of catecholamines may be complicated by mixed beta-adrenoceptor populations in the cat cardiovascular system.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects*; D002395:Catecholamines / Q000494:pharmacology*; D002396:Catechols; D002415:Cats; D004347:Drug Interactions; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D007545:Isoproterenol / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008771:Nordefrin / Q000031:analogs & derivatives*; D009638:Norepinephrine / Q000494:pharmacology; D010627:Phenethylamines / Q000494:pharmacology; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D002396:Catechols; D010627:Phenethylamines; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C011595:colterol; C018420:Ro 363; D007545:Isoproterenol; D008771:Nordefrin; D009638:Norepinephrine; D004837:Epinephrine