Participation of alpha 1- and beta 1-adrenoceptors in norepinephrine-induced contraction and relaxation of isolated equine coronary artery in vitro.
In coronary arterial rings isolated from horse, norepinephrine (NE)(10(-7) - 10(-5) M) induced concentration-dependent contractions which were not influenced by endothelial denudation. Prazosin (alpha 1-antagonist) inhibited the contraction, but yohimbine (alpha 2-antagonist) did not, and propranolol (beta-antagonist) enhanced the contraction. Pretreatment with phentolamine (10(-5) M) (alpha-antagonist) converted the contraction induced by NE to relaxation in coronary rings precontracted with ONO11113 (thromboxane A2 derivative). The relaxation was not influenced by removal of the endothelium, and was inhibited by propranolol and atenolol (beta 1-antagonist) but not by butoxamine (beta 2-antagonist). These results suggest that in equine coronary arteries, the contractile response to NE is mediated by stimulation of alpha 1-adrenoceptors on the smooth muscle, and that stimulation of beta 1-adrenoceptors on the smooth muscle modifies the contraction by inducing relaxation.
Obi
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Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, Japan.
Kabeyama
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Nishio
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D058668:Adrenergic alpha-1 Receptor Antagonists; D058671:Adrenergic beta-1 Receptor Antagonists; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D002078:Butoxamine / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006736:Horses; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D058671:Adrenergic beta-1 Receptor Antagonists; D018340:Receptors, Adrenergic, alpha-1; D018342:Receptors, Adrenergic, beta-1; D002078:Butoxamine; D015016:Yohimbine; D001262:Atenolol; D013928:Thromboxane A2; C037866:STA 2; D011433:Propranolol; D009638:Norepinephrine; D010646:Phentolamine