Calcium Signaling is important in signal transduction process, and involved in various physiological processes: cell growth, cell difference,etc. Ca2+ require the presence of specific intracellular Ca2+-binding proteins to exert their regulatory roles. A change in intracellular free calcium is a common signaling mechanism that modulates a wide array of physiological processes in most cells. Neuronal activity can lead to marked increases in the concentration of cytosolic calcium, which then functions as a second messenger that mediates a wide range of cellular responses. Ca2+ binds to calcium binding proteins (calmodulin/CaM) and stimulates the activity of a variety of enzymes, including CaM kinases and calcium-sensitive adenylate cyclases. These enzymes transduce the calcium signal and effect short-term biological responses, such as the modification of synaptic proteins and long-lasting neuronal responses that require changes in gene expression.