G-protein coupled receptor for octopamine (OA), which is a neurotransmitter, neurohormone, and neuromodulator in invertebrates. Activation of this receptor by octopamine induces an increase in both inositol phosphates and cyclic AMP. The coupling to adenylyl cyclase seems to be less efficient than the coupling to phospholipase C. The rank order of potency for agonists is p-synephrine >= clonidine > p-octopamine = xylometazoline = phenylephrine = oxymetazoline > B-HT920 > serotonin = p-tyramine > epinephrine > norepinephrine > methoxamine = dopamine = histamine. For antagonists, the rank order is yohimbine > chlopromazine / spiperone > phentolamine > mianserine > rauwolscine > prazosin > alprenolol / propanolol > pindolol. Expressed in the central nervous system. Belongs to the G-protein coupled receptor 1 family.