Competitive calcium binding: implications for dendritic calcium signaling

J Comput Neurosci. 1998 Jul;5(3):331-48. doi: 10.1023/a:1008891229546.


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 reaction partners within the compartment. Using the Ca2+ buffer EGTA as a competitor of fluo-3, we demonstrate competitive Ca2+ binding within dendrites experimentally. Nonequilibrium calcium dynamics is proposed as a potential mechanism for differential and conditional activation of intradendritic targets.

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Animals
  • Binding, Competitive / physiology
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Calcium-Binding Proteins / metabolism*
  • Chelating Agents / pharmacology
  • Dendrites / chemistry
  • Dendrites / physiology*
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Excitatory Postsynaptic Potentials / physiology
  • Kinetics
  • Models, Neurological*
  • Neocortex / cytology
  • Rats
  • Rats, Wistar
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*


  • Calcium-Binding Proteins
  • Chelating Agents
  • Egtazic Acid
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium