Competitive Calcium Binding: Implications for Dendritic Calcium Signaling

Action potentials evoke calcium transients in dendrites of neocortical pyramidal neurons with time constants of <100 ms at physiological temperature. This time period may not be sufficient for inflowing calcium ions to equilibrate with all present Ca2+ -binding molecules. We therefore explored nonequilibrium dynamics of Ca2+ binding to numerous Ca2+ reaction partners within a dendritelike compartment using numerical simulations. After a brief Ca2+ influx, the reaction partner with the fastest Ca2+ binding kinetics initially binds more Ca2+ than predicted from chemical equilibrium, while companion reaction partners bind less. This difference is consolidated and may result in bypassing of slow reaction partners if a Ca2+ clearance mechanism is active. On the other hand, slower reaction partners effectively bind Ca2+ during repetitive calcium current pulses or during slower Ca2+ influx. Nonequilibrium Ca2+ distribution can further be enhanced through strategic placement of the reac...

• Type: Journal
• Year: 1998
• Where: JCNS
• Authors: Henry Markram, Arnd Roth, Fritjof Helmchen
• Keywords: Ca2+, Calcium, JCNS 1998, Reaction Partners