Beta-adrenergic activities of octopamine and synephrine stereoisomers on guinea-pig atria and trachea.
The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on beta 1- and beta 2-adrenoceptors in guinea-pig atria and trachea have been compared with that of noradrenaline. The rank order of potency of the (-)-forms on beta 1-adrenoceptors was noradrenaline greater than m-synephrine greater than m-octopamine = p-octopamine greater than p-synephrine. m-Synephrine was 100-fold, m- and p-octopamine about 6000-fold, and p-synephrine about 40,000-fold less active than noradrenaline. The (+)-forms were 1-2 orders of magnitude less active than their (-)-counterparts. The four (-)-compounds were more than four orders of magnitude less active than noradrenaline on beta 2-adrenoceptors, and the (+)-forms had no detectable activity in concentrations as high as 10(-4) M. If m- and p-octopamine are co-released with noradrenaline in amounts proportional to their concentration, their activities at these structures are too low to be physiologically significant.
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D000818:Animals; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D009655:Octopamine / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013237:Stereoisomerism; D013578:Synephrine / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D009655:Octopamine; D013578:Synephrine