A probe for octopamine receptors: synthesis of 2-[(4-azido-2,6-diethylphenyl)imino]imidazolidine and its tritiated derivative, a potent reversible-irreversible activator of octopamine-sensitive adenylate cyclase.

In order to develop an irreversible ligand for octopamine receptors, a highly potent azido-substituted 2-(phenyl-imino)imidazolidine (NC-5Z, 8) and its tritiated derivative (3H-NC-5Z, 11) have been designed and synthesized. Under reversible-binding conditions, NC-5Z is 50-100-fold more potent than octopamine in activating octopamine-sensitive adenylate cyclase in a variety of tissues. After photolysis, 3H-NC-5Z binds irreversibly to cell membranes, and this binding is reduced by preincubation with octopamine agonists and antagonists but not by norepinephrine, dopamine, serotonin, or histamine. NC-5Z should be useful both as a potent reversible octopamine agonist and as an affinity probe for characterizing and isolating octopamine-receptor proteins.