Fractional contribution of calcium to the cation current through glutamate receptor channels

Neuron. 1993 Jul;11(1):133-43. doi: 10.1016/0896-6273(93)90277-x.


The Ca2+ fraction of the ion current flowing through glutamatergic NMDA and AMPA/kainate receptor channels was determined in forebrain neurons of the medial septum. The neurons were overloaded with the Ca2+ indicator dye fura-2 (1 mM) via the recording patch pipettes. This approach allowed the direct determination of the Ca2+ influx from changes in the Ca(2+)-sensitive fura-2 fluorescence. We found that, at negative membrane potentials and at an extracellular free Ca2+ concentration of 1.6 mM, the Ca2+ fraction of the current through the NMDA receptor channels is only 6.8%, about 2-fold lower than previously estimated from reversal potential measurements. Interestingly, a quite high fractional Ca2+ current of 1.4% was determined for the linearly conducting AMPA/kainate receptor channels found in these neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium / physiology*
  • Cations / metabolism*
  • Electric Conductivity
  • Electrophysiology
  • Ion Channels / physiology*
  • Neurons / metabolism
  • Rats
  • Rats, Wistar
  • Receptors, AMPA
  • Receptors, Glutamate / metabolism
  • Receptors, Glutamate / physiology*
  • Receptors, Kainic Acid
  • Receptors, N-Methyl-D-Aspartate / metabolism
  • Septum Pellucidum / cytology
  • Septum Pellucidum / metabolism


  • Cations
  • Ion Channels
  • Receptors, AMPA
  • Receptors, Glutamate
  • Receptors, Kainic Acid
  • Receptors, N-Methyl-D-Aspartate
  • Calcium