Effect of the amino-oxazoline derivative S-3341 on pre- and postjunctional alpha-adrenoceptors in isolated blood vessels.
In segments of isolated dog saphenous veins, S-3341 (10(-8) to 10(-4) M) induced concentration-dependent contractions which, like those to clonidine, were progressively inhibited by increasing concentrations of yohimbine (10(-8) to 10(-6) M) but not by prazosin (10(-8) to 10(-6) M). In strips of the rabbit main pulmonary artery, previously labelled with [3H]noradrenaline and mounted for superfusion, S-3341 and clonidine both decreased the overflow of [3H] caused by electrical stimulation; these effects of S-3341 and clonidine were inhibited by 10(-6) M of yohimbine but not by 10(-6) M of prazosin. Our results illustrate that both S-3341 and clonidine cause contraction by activation of postjunctional alpha 2-adrenoceptors and decrease noradrenaline-release by stimulating prejunctional alpha 2-adrenoceptors. At the postjunctional alpha 2-adrenoceptors clonidine is 27 times more potent than S-3341, while at the prejunctional alpha 2-adrenoceptors, clonidine is only 15 times more potent than S-3341.
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D004285:Dogs; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000378:metabolism; D010080:Oxazoles / Q000494:pharmacology*; D010477:Perfusion; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D000077769:Rilmenidine; D012501:Saphenous Vein / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D010080:Oxazoles; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; D003000:Clonidine; D000077769:Rilmenidine; D009638:Norepinephrine; D011224:Prazosin