Orphan receptor. Displays a significant level of constitutive activity. Its effect is mediated by G(s)-alpha protein that stimulate adenylate cyclase, resulting in an elevation of intracellular cAMP. High level of expression in placenta. Expressed throughout the brain at low level. No expression detected in skeletal muscle, lung, heart, liver, pancreas, or kidney. Belongs to the G-protein coupled receptor 1 family.