title: Pharmacological analysis of the postjunctional alpha-adrenoceptors of the rat anococcygeus muscle and vas deferens.
abstract: The alpha-adrenoceptor sub-type of the rat vas deferens was characterized with noradrenaline (alpha-1, alpha-2-agonist), phenylephrine (alpha-1-agonist), prazosin (alpha-1-antagonist) and yohimbine (alpha-2-antagonist) and compared with the results obtained in the rat anococcygeus muscle. In the vas deferens, both prazosin and phentolamine were competitive antagonists of noradrenaline and phenylephrine whereas yohimbine was a non-competitive antagonist irrespective of the concentrations of these antagonists. On the other hand, in the anococcygeus muscle, at low concentrations, prazosin was non-competitive against noradrenaline whilst it was competitive against phenylephrine. Yohimbine behaved as a competitive antagonist of noradrenaline at both low and high concentrations whilst at low concentrations it was non-competitive against phenylephrine. These results suggest a predominance of alpha-1-adrenoceptors in the vas deferens located postjunctionally with a small population of alpha-2-subtype adrenoceptors, whilst the anococcygeus muscle seems to contain relatively more alpha 2-adrenoceptors postjunctionally than the vas deferens.
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D009928:Organ Specificity; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine