D(1B) dopamine receptor is a protein of the dopamine receptor. The D₅ subtype is a G-protein coupled receptor which stimulates adenylyl cyclase. This receptor is expressed in neurons in the limbic regions of the brain. It has a 10-fold higher affinity for dopamine than the D₁ subtype. Pseudogenes related to this gene reside on chromosomes 1 and 2.The D₁ and D₅ receptors have a high degree of structural homology and few ligands are available that can distinguish between them as yet, however there are a number of ligands that are selective for D_1/5 over the other dopamine receptors. The recent development of a selective D₅ antagonist has allowed the action of D₁-mediated responses to be studied in the absence of a D₅ component, but no selective D₅ agonists are yet available.