Adrenergic activity of ortho-, meta-, and para-octopamine

DL-o-, and p-octopamine were tested for beta- and alpha-adrenergic activity in rats. When compared to DL-isoproterenol, a beta-adrenergic agonist, all three isomers failed to show significant beta-adrenergic activity as assessed by intiation of thirst and by increase in tail skin temperature. All three isomers increased mean blood pressure in pentolinium-blocked rats. Of the three 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 :0.0007 for norepinephrine, m-, p- and o-octopamine, respectively. Thus, DL-m-octopamine has about 1/100th the alpha-adrenergic activity of L-norepinephrine.