title: Assessment of alpha-adrenergic receptor subtypes in isolated rat aortic segments.
abstract: The postsynaptic alpha-adrenoceptors in the isolated rat aorta have been characterized according to the sensitivity of the tissue to selective alpha 1- and alpha 2-adrenoceptor agonists and antagonists. The potency (-log EC50) order of the non-selective alpha-agonist norepinephrine and relatively selective agonists was as follows: norepinephrine (alpha 1 = alpha 2; 7.30); clonidine (alpha 2 greater than alpha 1; 7.01); phenylephrine (alpha 1 greater than alpha 2; 6.99), SK & F 89748--A (alpha 1 greater than alpha 2; 6.65); BHT-920 (alpha 2 much greater than alpha 1; 5.56) and M-7 (alpha 2 greater than alpha 1; 4.66). The isolated rat aorta was 12-200-fold more sensitive to the alpha 1-adrenoceptor agonists phenylephrine and SK & F 89748-A, than to the alpha 2-agonists, BHT-920 and M-7. Prazosin is 245-1259-fold more potent than rauwolscine as an antagonist of contractions induced by various alpha 1- and alpha 2-agonists in the rat aorta. These data indicate that constriction of the smooth muscle of the rat aorta to alpha-adrenergic agonists is mediated through alpha 1- but not alpha 2-adrenoceptors.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D001381:Azepines / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009284:Naphthols / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D001381:Azepines; D009284:Naphthols; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; C009957:5,6-dihydroxy-2-dimethylaminotetralin; C024763:talipexole; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin