P2RY6 and astrocytoma (excluding glioblastoma): ADP has been shown to elicit a calcium response in 1321N1 astrocytoma cells over-expressing P2Y6 receptors, but its effects are much less potent than the preferred agonist of P2Y6 receptors, UDP [36], so it was surprising that MRS2578 abolished the response to ADP in MSCs, when these cells lack a UDP-elicited Ca2+ response.