Figure 2.

Sources of cytosolic Ca²⁺ in vesicular release from astrocytes. Increase of cytosolic Ca²⁺ is sufficient and necessary to cause vesicular fusions and release of gliotransmitters. This process of regulated exocytosis requires the action of the ternary SNARE complex. Cytosolic Ca²⁺ accumulation could be caused by the entry of Ca²⁺ from the ER internal stores via IP₃ and ryanodine receptors (IP₃ and RyR). Store specific Ca²⁺-ATPase fills these stores, although ultimately this action requires Ca²⁺ entry from the extracellular space (ECS) through canonical type 1 transient receptor potential (TRPC1). Mitochondrial Ca²⁺ uptake is mediated by the uniporter, while free Ca²⁺within the mitochondrial matrix exits through the Na⁺/ Ca²⁺ exchanger and the mitochondrial permeability transition pore (MPTP). Drawing is not to scale.