title: Involvement of alpha-adrenoceptors in the endothelium-dependent depression of noradrenaline-induced contraction in rat aorta.
abstract: The involvement of endothelium-derived nitric oxide (NO) in the depressant action of the endothelium on noradrenaline-induced contractions and characterization of the receptor involved in the release of NO were studied using rat aorta. The noradrenaline-induced contraction was significantly potentiated by endothelium removal and in the presence of NG-nitro-L-arginine (L-NNA) or NG-monomethyl-L-arginine (L-NMMA). The contraction induced by phenylephrine was also potentiated in the presence of L-NNA. Clonidine could induce contraction only in endothelium-denuded preparations or in the presence of L-NNA. The potentiating action of L-NNA on noradrenaline-induced contractions could also be observed in the presence of yohimbine or rauwolscine, although dose-response curves were shifted to the right. The depression of noradrenaline-induced contractions observed in the presence of the endothelium was increased by repeated stimulation. The depression was prevented by L-NNA and this effect was reversed by L-arginine. These results indicate the possibility that NO can be released through stimulation of alpha 1- and alpha 2-adrenoceptors on the endothelium and depresses noradrenaline-induced contractions of smooth muscle, although the contribution of the respective adrenoceptors remains to be investigated. The release of NO was increased when the stimulation was applied repeatedly.
authors.affiliation: Research Institute of Hypertension, Kinki University, Osaka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kaneko
authors.forename: S
authors.initials: S
authors.lastname: Sunano
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine; D009638:Norepinephrine / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology; D019323:omega-N-Methylarginine
chemical_list: D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D019335:Nitroarginine; D019323:omega-N-Methylarginine; D015016:Yohimbine; D009569:Nitric Oxide; D001120:Arginine; D003000:Clonidine; D009638:Norepinephrine