On the basis of pharmacological, sequence and cellular signaling criteria, at least three groups of octopamine GPCR have been defined. OctαR (OCTOPAMINE₁ receptors) are more closely related to α-adrenergic receptors. OctβR (OCTOPAMINE₂ receptors) are more closely related to β-adrenergic receptors. A third group (of which Oct-TyrR is a member) the Octopamine/Tyramine receptors can bind both ligands, and display agonist-specific coupling. Oct-TyrR is therefore listed in both OCTOPAMINE and TYRAMINE RECEPTORS gene groups (FBrf0221114).