Ca2+ buffering and action potential-evoked Ca2+ signaling in dendrites of pyramidal neurons

Biophys J. 1996 Feb;70(2):1069-81. doi: 10.1016/S0006-3495(96)79653-4.


The effect of the fluorescent Ca2+ indicator dye Fura-2 on Ca2+ dynamics was studied in proximal apical dendrites of neocortical layer V and hippocampal CA1 pyramidal neurons in rat brain slices using somatic whole-cell recording and a charge-coupled device camera. A single action potential evoked a transient increase of intradendritic calcium concentration ([Ca2+]i) that was reduced in size and prolonged when the Fura-2 concentration was increased from 20 to 250 microM. Extrapolation to zero Fura-2 concentration suggests that "physiological" transients at 37 degrees C have large amplitudes (150-300 nM) and fast decays (time constant < 100 ms). Assuming a homogeneous compartment model for the dendrite, 0.5-1% of the total Ca2+ entering during an action potential was estimated to remain free. Washout of cytoplasmic Ca2+ buffers was not detectable, suggesting that they are relatively immobile. During trains of action potentials, [Ca2+]i increased and rapidly reached a steady state (time constant < 200 ms), fluctuating around a plateau level which depended linearly on the action potential frequency. Thus, the mean dendritic [Ca2+]i encodes the action potential frequency during physiological patterns of electrical activity and may regulate Ca(2+)-dependent dendritic functions in an activity-dependent way.

MeSH terms

  • Action Potentials
  • Animals
  • Biophysical Phenomena
  • Biophysics
  • Buffers
  • Calcium / metabolism*
  • Cell Compartmentation
  • Dendrites / metabolism*
  • Fluorescent Dyes
  • Fura-2
  • In Vitro Techniques
  • Indicators and Reagents
  • Kinetics
  • Models, Neurological
  • Pyramidal Cells / metabolism*
  • Rats
  • Rats, Wistar
  • Signal Transduction


  • Buffers
  • Fluorescent Dyes
  • Indicators and Reagents
  • Calcium
  • Fura-2