Controlling the urge for a Ca²⁺ surge: All-or-none Ca²⁺ release in neurons

Changes in the intracellular calcium concentration ([Ca²⁺](i)) convey signals that are essential to the life and death of neurons. Ca²⁺-induced Ca²⁺-release (CICR), a process in which a modest elevation in [Ca²⁺](i) is amplified by a secondary release of Ca²⁺ from stores within the cell, plays a prominent role in shaping neuronal [Ca²⁺](i) signals. When CICR becomes regenerative, an explosive increase in [Ca²⁺](i) generates a Ca2⁺ wave that spreads throughout the cell. A discrete threshold controls activation of this all-or-none behavior and cellular context adjusts the threshold. Thus, the store acts as a switch that determines whether a given pattern of electrical activity will produce a local or global Ca²⁺ signal. This gatekeeper function seems to control some forms of Ca²⁺-triggered plasticity in neurons.