Adrenergic Activity of Ortho-, Meta-, and Para-Octopamine

Abstract

DL-o-,m- and p-Octopamine were tested for .beta.- and .alpha.-adrenergic activity in rats. When compared to DL-isoproterenol, a .beta.-adrenergic agonist, the 3 isomers did not show significant .beta.-adrenergic activity as assessed by thirst initiation and by increase in tail skin temperature. All 3 isomers increased mean blood pressure in pentolinium-blocked rats. Of the 3 isomers m-octopamine possessed the greatest .alpha.-adrenergic activity. When the responses were compared with those induced by L-norepinephrine the order of activities was: 1:0.01:0.0005:0.00007 for norepinephrine, m-,p- and o-octopamine, respectively. DL-m-Octopamine has about 1/100th the .alpha.-adrenergic activity of L-norepinephrine.