Increase of the intracellular Ca2+ concentration mediated by transport of glutamate into rat hippocampal synaptosomes: characterization of the activated voltage sensitive Ca2+ channels

Neurochem Int. 1998 Jan;32(1):7-16. doi: 10.1016/s0197-0186(97)00048-x.


The changes in the intracellular free Ca2+ concentration, [Ca2+]i, mediated by glutamate and D-aspartate into rat hippocampal synaptosomes was studied. Glutamate increased the [Ca2+]i in a dose-dependent manner with an EC50 of 1.87 microM and a maximal increase of 31.5 +/- 0.9 nM. We also observed that stimulation of the synaptosomes with 100 microM alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), 100 microM kainate, or 100 microM D-aspartate increased the synaptosomal [Ca2+]i. The effect of either of these non-NMDA receptor agonists and of D-aspartate was additive, suggesting the activation of two different components (the ionotropic non-NMDA receptors or the glutamate transporters). Stimulation of synaptosomes with 100 microM glutamate increased the [Ca2+]i and prevented the effect of either non-NMDA receptor agonists and the effect of D-aspartate. We also observed that incubation of the synaptosomes with D-aspartate induced the Ca(2+)-independent release of glutamate, possibly through the reversal of the glutamate carrier. The aim of incubating the synaptosomes with D-aspartate was to avoid undesirable secondary activation of glutamate receptors. After incubating the synaptosomes with 100 microM D-aspartate (10 min at 37 degrees C), the subsequent stimulation with D-aspartate increased the [Ca2+]i due to glutamate transport. This increase in [Ca2+]i induced by 100 microM D-aspartate was insensitive to 1 microM nitrendipine, but was inhibited by about 50% by the presence of both 500 nM omega-CgTx GVIA and 100 nM omega-Aga IVA or by 500 nM omega-CgTx MVIIC. We clearly identified two different processes by which glutamate increased the [Ca2+]i in rat hippocampal synaptosomes: activation of non-NMDA receptors and activation of the glutamate transporters. We also characterized the voltage sensitive Ca2+ channels (VSCC) activated as a consequence of the glutamate transport, and determined that class B (N-type) and class A (P or Q-type) Ca2+ channels were responsible for about 50% of the signal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / physiology
  • Amino Acid Transport System X-AG
  • Animals
  • Aspartic Acid / pharmacology
  • Biological Transport
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / physiology*
  • Glutamic Acid / metabolism*
  • Glutamic Acid / pharmacology
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Kainic Acid / pharmacology
  • Male
  • Peptides / pharmacology
  • Rats
  • Rats, Wistar
  • Receptors, Glutamate / physiology
  • Spider Venoms / pharmacology
  • Synaptosomes / drug effects
  • Synaptosomes / metabolism*
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology
  • omega-Agatoxin IVA
  • omega-Conotoxin GVIA
  • omega-Conotoxins*


  • ATP-Binding Cassette Transporters
  • Amino Acid Transport System X-AG
  • Calcium Channel Blockers
  • Calcium Channels
  • Peptides
  • Receptors, Glutamate
  • Spider Venoms
  • omega-Agatoxin IVA
  • omega-Conotoxins
  • omega-conotoxin-MVIIC
  • Aspartic Acid
  • Glutamic Acid
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
  • omega-Conotoxin GVIA
  • Kainic Acid
  • Calcium