Dopamine Receptor
All known physiological effects of dopamine are mediated by five dopamine receptors (D1-D5), Class A GPCRs encoded by DRD1-DRD5. They organize into two pharmacologically distinct branches: the D1-like subfamily (D1 and D5) couples to Gs/Golf and stimulates adenylyl cyclase, whereas the D2-like subfamily (D2, D3 and D4) couples to Gi/o and inhibits cAMP production. These receptors control movement, motivation, reward and endocrine regulation: D2 agonists treat Parkinson's disease and hyperprolactinemia, while D2 antagonism underlies most antipsychotic drugs, whose efficacy and extrapyramidal side effects both track with striatal D2 occupancy. DRD2 is also the principal target of the dopaminergic agents used in restless legs syndrome.
