Figure 2. Melatonin (MT) receptors and their pathways. Abbreviations: MT, melatonin; R, melatonin receptor; AC, Adenylyl Cyclase; ATP, adenosine triphosphate; cAMP, cyclic adenosine monophosphate; PKA, protein kinase A; CREB, responsive element binding protein; PLC, phospholipase C; PIP2, phosphatidylinositol 4,5-bisphosphate; DAG, diacylglycerol; CG, guanylyl Cyclase; GTP, guanosine triphosphate; and GMP, guanosine monophosphate [