title: No evidence for differences between pre- and post-junctional alpha 2-adrenoceptors.
abstract: We have examined the pre- and post-junctional effects of a series of alpha-adrenoceptor agonists and antagonists at alpha 2-adrenoceptors in the pithed rat preparation and the human isolated saphenous vein. In the pithed rat, there was no difference in relative agonist and antagonist potencies between pre- and post-junctional alpha 2-adrenoceptors but the absolute potencies of antagonists differed: antagonists were more potent prejunctionally. In the human saphenous vein, the alpha 2-adrenoceptor antagonist yohimbine had pre- and post-junctional actions over the same concentration range. We have no evidence to suggest differences between pre- and post-junctional alpha 2-adrenoceptors: differences in absolute antagonist potencies in the pithed rat may be due to non-equilibrium conditions.
authors.forename: J R
authors.initials: JR
authors.lastname: Docherty
authors.forename: L
authors.initials: L
authors.lastname: Hyland
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003655:Decerebrate State; D006801:Humans; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012501:Saphenous Vein / Q000187:drug effects / Q000294:innervation; D013997:Time Factors
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D011224:Prazosin