The agonist action of substituted phenylethanolamines on octopamine receptors in cockroach ventral nerve cords

1. Effect of 72 ring or α-substituted phenylethanolamines (SPEAs) was examined on the adenylate cyclase prepared from ventral nerve cords of the American cockroach Periplaneta americana. 2. Para-Cl-SPEA was the most effective octopaminergic agonist, followed by p-Br-, p-F-, p-Me-, p-NO₂- and p-CF₃-SPEA. 3. Meta- and o-SPEAs were less active than p-SPEAs, in stimulating adenylate cyclase. 4. SPEA analogs interact with the same binding site as octopamine in the nerve cords of American cockroach, since the level of evoked cAMP production by a combination of optimally effective concentrations of octopamine and SPEA was not greater than the stimulation by octopamine alone. 5. Washing removed nearly all of the stimulatory activity of SPEA, suggesting that SPEA binds reversibly to the octopaminergic receptor.