In contrast to the ion channel P2X receptors, P2YRs are activated by several endogenous ligands including the adenine nucleotides: ADP (acting on P2Y1, P2Y12, and P2Y13) and ATP (acting on P2Y2 and P2Y11), and the uridine nucleotides UTP (acting on P2Y2 and P2Y4), UDP (acting on P2Y6), and the UDP-glucose (acting on P2Y14).222
