title: Effects of alpha-adrenoceptor agents on norepinephrine release from vas deferens of several species including man.
abstract: Unlike the situation with the vas deferens of rats, guinea-pigs, rabbits and dogs, neither phentolamine nor yohimbine enhanced electrically-evoked release of [3H]norepinephrine from the in vitro human vas deferens. However, clonidine produced, by a phentolamine-sensitive mechanism, a concentration-related inhibition of release in the human vas deferens. The results indicate that, even though presynaptic alpha-adrenoceptors exist, a negative feedback regulation of release by norepinephrine, which occurs in the vas deferens of the other species, may not be functionally important in the vas deferens of the human.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004285:Dogs; D006168:Guinea Pigs; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010646:Phentolamine / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013552:Swine; D014649:Vas Deferens / Q000378:metabolism
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D009638:Norepinephrine; D010646:Phentolamine