title: Relative agonist potency as a means of differentiating alpha-adrenoceptors and alpha-adrenergic mechanisms.
abstract: Relative potencies (ED50), affinities (assessed as dissociation constants) and efficacies (i.e. ability to activate the receptor) of agonists are useful in subclassifying and differentiating alpha-adrenoceptors. The postsynaptic alpha-adrenoceptor of rat aorta is of the alpha 1-subtype, but may differ from the alpha 1-adrenoceptor of rabbit and guinea pig aortae, based on comparison of relative potencies of selected agonists. By evaluating the relative potency of agonists, qualitative and quantitative species differences between alpha 1-adrenoceptors in rat and guinea pig are observed in a variety of test systems in vivo and in vitro. By comparing the relative potencies of aromatic hydroxyl-substituted phenethylamines and imidazolines at alpha 1-adrenoceptors in guinea pig aorta, differences in the ability of these two classes of alpha-adrenoceptor agonists to bind to, and subsequently activate, alpha 1-adrenoceptors have been observed. Evaluating the relative potencies of agonists, when used in conjunction with other techniques, provides a valuable method for classifying alpha-adrenoceptors and for studying alpha-adrenergic mechanisms.
authors.forename: R R
authors.initials: RR
authors.lastname: Ruffolo
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000032:analysis; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D010627:Phenethylamines / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000032:analysis / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity; D013237:Stereoisomerism
chemical_list: D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; D010627:Phenethylamines; D011942:Receptors, Adrenergic, alpha