Prostanoids are a series of arachidonic acid metabolites produced by the action of cyclooxygenase and subsequently by isomerases and synthases. Cells rapidly secrete prostanoids after synthesis, whereupon the prostanoids bind to a family of 8 GPCRs to exert their biological effects. The prostaglandin PGF2alpha binds specifically to the FP receptor, which couples to Gq/11 to mobilize intracellular calcium. Binding of PGF2alpha to FP receptors in the corpus luteum is required for luteolysis and subsequent parturition in mice. PGF2alpha also decreases intraocular pressure by an FP-dependent mechanism, and an PGF2--analog--latanoprost, is used clinically in the treatment of glaucoma. FP also contributes to tachycardia induced by inflammatory stimuli.