Receptor for prostaglandin D2 (PGD2). The activity of this receptor is mainly mediated by G(s) proteins that stimulate adenylate cyclase, resulting in an elevation of intracellular cAMP. A mobilization of calcium is also observed, but without formation of inositol 1,4,5-trisphosphate (PubMed:10448933). Involved in PLA2G3-dependent maturation of mast cells. PLA2G3 is secreted by immature mast cells and acts on nearby fibroblasts upstream to PTDGS to synthesize PGD2, which in turn promotes mast cell maturation and degranulation via PTGDR (By similarity). Strongly expressed in eye and gastrointestinal tract (GIT), moderately in the brain and oviduct and weakly in the epididymis. In the eye, expressed in the epithelium of the iris and ciliary body and in photoreceptor cells of the retina. In the brain, expressed in leptomeninges, choroid plexus and spinal cord (sensory and motor neurons of the dorsal and ventral horns). In the stomach, expressed in the mucous-secreting goblet cells and the columnar epithelium. Expressed in platelets. Belongs to the G-protein coupled receptor 1 family.