Characterization of insect neuronal octopamine receptors (OA3 receptors).

Octopamine receptors in the nervous tissue of insects were investigated using a ligand-receptor assay with [3H]NC-5Z or [3H]octopamine as the radioligands. Both ligands recognized a homogeneous class of binding sites with the properties of an octopamine receptor. This receptor has been characterized pharmacologically. Both high-affinity agonists (e.g. NC 7, K1 = 0.3 nM) and antagonists (e.g. maroxepine, K1 = 1.02 nM) were investigated. The neuronal octopamine receptor belongs to a receptor class that can easily be distinguished from peripheral octopamine receptors. Initial investigations of the localization of octopamine receptors within the insect nervous tissue show the greatest receptor density in the optic lobes.