Dopamine Receptor Antibodies

The dopamine receptor family comprises five class A G protein-coupled receptors that share dopamine as their endogenous agonist. The D₁-like receptors (D₁ and D₅) couple primarily to Gs or Golf and stimulate adenylyl cyclase, whereas the D₂-like receptors (D₂, D₃, and D₄) couple primarily to Gi/o and inhibit cAMP production. D₁ and D₂ receptors are abundant in the striatum, where they regulate basal ganglia circuits involved in movement and action selection. D₃ receptors are enriched in limbic circuits associated with motivation and reward, while D₄ and D₅ receptors are expressed in regions that include the prefrontal cortex and hippocampus, respectively. Presynaptic D₂ autoreceptors provide feedback inhibition of dopamine synthesis and release, while pituitary D₂ receptors suppress prolactin secretion. Agonist exposure can induce receptor phosphorylation, β-arrestin recruitment, and internalization, with the extent and timing of these responses varying by subtype and ligand. Clinically used agonists include pramipexole and ropinirole for Parkinson’s disease and cabergoline for hyperprolactinemia. D₂ receptor antagonists such as haloperidol and partial agonists such as aripiprazole are used to treat schizophrenia. Fenoldopam, a peripheral D₁-like receptor agonist, is used intravenously for short-term blood pressure reduction in severe hypertension.