Dependence of calcium influx in neocortical cells on temporal structure of depolarization, number of spikes, and blockade of NMDA receptors

J Neurosci Res. 2004 May 15;76(4):481-7. doi: 10.1002/jnr.20104.


Increase of intracellular [Ca(2+)] evoked by action potentials in a cell can induce long-term synaptic plasticity even without concomitant presynaptic stimulation. We used optical recording of the fluorescence of a Ca(2+)-indicator Oregon Green to investigate whether differences in results obtained with modifications of that purely postsynaptic induction protocol could be due to differential Ca(2+) influx. We compared changes of the somatic [Ca(2+)] in layer II-III pyramidal cells in slices of rat visual cortex evoked by bursts of depolarization pulses and long depolarizing steps. During weak depolarizations, the Ca(2+) influx was proportional to the amplitude and duration of the depolarization. With suprathreshold depolarizations, the Ca(2+) influx was proportional to the number of action potentials. Because the burst depolarizations evoked more spikes than did the long duration steps, this burst protocol led to a larger Ca(2+) influx. With all stimulation protocols, the spike-induced Ca(2+) influx was reduced during blockade of N-methyl-D-aspartate (NMDA) receptors. Differences in intracellular [Ca(2+)] increases thus may be one reason for differential effects of purely postsynaptic challenges on synaptic transmission.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Animals
  • Calcium / metabolism*
  • Electric Stimulation / methods
  • Fluorescent Dyes / metabolism
  • In Vitro Techniques
  • Membrane Potentials / physiology
  • Neurons / drug effects
  • Neurons / physiology*
  • Organic Chemicals
  • Patch-Clamp Techniques / methods
  • Rats
  • Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors*
  • Valine / analogs & derivatives*
  • Valine / pharmacology*
  • Visual Cortex / cytology*


  • Fluorescent Dyes
  • Oregon Green BAPTA-dextran
  • Organic Chemicals
  • Receptors, N-Methyl-D-Aspartate
  • 2-amino-5-phosphopentanoic acid
  • Valine
  • Calcium