DRD1 (Dopamine receptor D1) is a G-protein coupled receptor and the most abundant dopamine receptor found in the central nervous system. DRD1 is primarily found in the dorsal striatum in the brain, where it regulates neuronal growth and modulates behavioral responses. In the hippocampus, DRD1 works with GHSR1a (growth hormone secretagogue receptor) to promote synaptic formation and this interaction can be disrupted and lead to synaptic injury in Alzheimer’s disease. Agonists to DRD1 are of interest in the treatment of neuropsychiatric diseases and neurodegenerative diseases including Parkinson’s, and can be associated with cognitive enhancements. In immunohistochemistry, DRD1 is expected to have membranous positivity in the brain. References: Neuropsychopharmacology. 40 (2): 446–453, PMID: 25074637; Clin Neuropharmacol. 21 (6): 339–43. PMID 9844789; Science Translational Medicine. 2019. Vol. 11 (505): eaav6278, DOI: 10.1126/scitranslmed.aav6278