Dopamine D3, D4, and D5 receptors (D3R, D4R, D5R)

Dopamine receptor D3, dopamine receptor D4, and dopamine receptor D5 are distinct subtypes of dopamine receptors, all belonging to the family of G protein-coupled receptors that mediate the effects of dopamine, a major neurotransmitter. D3 and D4 are part of the D2-like subfamily, primarily coupling via Gi/o proteins to inhibit adenylyl cyclase and reduce cAMP levels; these receptors are mainly found in brain regions involved in mood, cognition, and reward pathways, and they are important therapeutic targets in psychiatric and neurological disorders. D5, by contrast, is a D1-like receptor, couples to Gs proteins, activates adenylyl cyclase, and increases cAMP; it shares high homology with the D1 receptor and is expressed in the CNS and some peripheral tissues. Genetic polymorphisms of DRD4 are associated with behavioral traits and psychiatric conditions such as ADHD. Drugs targeting these receptors include antipsychotics, dopaminergic agonists, and experimental agents, but significant therapeutic and safety challenges arise due to their role in diverse physiological functions and broad tissue expression.

Other names

DRD3Dopamine D3 receptorDRD4Dopamine D4 receptorDRD5Dopamine D5 receptor

D3/D4: Drugs act as agonists or antagonists, mainly influencing the inhibition of adenylyl cyclase via Gi/o protein coupling, reducing cAMP production. Antagonists (e.g., antipsychotics) block dopaminergic signaling; agonists (e.g., used in Parkinson’s disease) stimulate receptor activity. D5: Agonists activate adenylyl cyclase via Gs coupling and increase cAMP; antagonists block this activation.