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

Changes in the intracellular calcium concentration ([Ca2+](i)) convey signa ls that are essential to the life and death of neurons. Ca2+-induced Ca2+-r elease (CICR), a process in which a modest elevation in [Ca2+](i) is amplif ied by a secondary release of Ca2+ from stores within the cell, plays a pro minent role in shaping neuronal [Ca2+](i) signals. When CICR becomes regene rative, an explosive increase in [Ca2+](i) generates a Ca2+ wave that sprea ds throughout the cell. A discrete threshold controls activation of this al l-or-none behavior and cellular context adjusts the threshold. Thus, the st ore acts as a switch that determines whether a given pattern of electrical activity will produce a local or global Ca2+ signal. This gatekeeper functi on seems to control some forms of Ca2+-triggered plasticity in neurons. (C) 1999 John Wiley & Sons, Inc.