Nucleotides are emerging as important extracellular signaling molecules that mediate several effects, such as proliferation, differentiation , chemotaxis and cytokine release. The P2 receptor family is activated by the binding of nucleotides and is divided into two subfamilies, P2X and P2Y. The P2X receptor family is comprised of ligand-gated ion channels that allow for the increased permeability of calcium into the cell in response to extracellular ATP. The P2Y receptor family are G protein-coupled receptors which mediate the effects of extracellular nucleotides, primarily through the activation of phospholipase C. To some extent, the P2Y receptors can also activate potassium channels or, alternatively, inhibit adenylate cyclase and N-type calcium channels in response to extracellular nucleotides. P2Y9 is activated by lysophosphatidic acid (LPA), a lipid mediator involved in cell proliferation, differentiation, survival and death. In hamsters, P2Y9 mRNA is significantly expressed in ovary tissue compared to other tissues, and innervation with 1-oleoly LPA increases intracellular calcium ion concentration and stimulates adenylyl cyclase activity. P2Y9 is structurally related to nucleotide receptors, and shares 20-24% amino acid homology with the three other LPA receptors (LPA1, LPA2, LPA3).