The function of GPR3 (G protein-coupled receptor 3, Ensembl gene identifier ENSG00000181773) is as follows. Constitutively active G protein-coupled receptor that maintains high cAMP levels and contributes to several processes, including meiotic arrest in oocytes and neuronal development, through activation of intracellular signaling pathways. Essential activator of thermogenic adipocytes, where it drives thermogenesis via constitutive G(s)-coupling activity in the absence of ligand (PubMed:34048700). May be activated by lipid-derived agonists such as oleoylethanolamide (OEA), oleic acid or sphingosine 1-phosphate leading to activation of the G(s)/cAMP/PKA signaling pathway (PubMed:12220620, PubMed:38376112, PubMed:38287117). Plays a potential role in modulating brain functions, including behavioral responses to stress and amyloid-beta peptide generation in neurons (By similarity). Stimulates neurite outgrowth in cerebellar granule neurons via PKA, ERK, and PI3K-mediated signaling pathways (By similarity). {ECO:0000250|UniProtKB:P35413, ECO:0000269|PubMed:12220620, ECO:0000269|PubMed:19213921, ECO:0000269|PubMed:34048700, ECO:0000269|PubMed:38287117, ECO:0000269|PubMed:38376112}.