Astrocytic calcium transients are primarily mediated through the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol (1,4,5) trisphosphate (IP3) following activation of G-protein coupled receptors. IP3 promotes the release of Ca2+ predominately from intracellular pools (endoplasmatic reticulum; ER), into the cytoplasm, and influx of calcium through calcium channels primarily activated by changes in membrane potential. Following formation/release of IP3 or Ca2+, these signaling molecules may spread to surrounding astrocytes through gap junction channels (Gjc) and lead to coordinated release of gliotransmitters.