Measured increase in intracellular Ca super(2+) during stimulated release of endogenous glutamate from human cerebrocortical synaptosomes

• Published in: Brain research 1999-10, Vol.843 (1-2), p.199-201
• Main Authors: Vinje, M L, Valoe, E T, Roeste, G K, Berg-Johnsen, J
• Format: Article
• Language: English
• ISSN: 0006-8993
• DOI: 10.1016/S0006-8993(99)01901-0

Presynaptic terminals (synaptosomes) prepared from guinea pig and rat cerebral cortex release endogenous glutamate in a Ca super(2+)-dependent manner in response to membrane depolarisation. In the present study, synaptosomes were prepared from human cerebral cortex removed in association with temporal lobe resections in epileptic patients. The cytosolic free Ca super(2+) concentration increased from 474 plus or minus 66 before to 649 plus or minus 89 nM after 2 min depolarisation. The basal level of free cytosolic Ca super(2+) is higher and the increase in response to depolarisation is more pronounced in human synaptosomes than observed in animal experiments. The Ca super(2+)-dependent glutamate release, estimated as the difference between total -- and the Ca super(2+)-independent glutamate release, increased from 0 to 5.4 plus or minus 1.9 nmol/mg protein. The released amount of glutamate is larger than reported in animal models. These results demonstrate that membrane depolarisation of synaptosomes from human brain evokes a rapid rise in cytosolic free Ca super(2+) and a more prolonged rise in synaptic, Ca super(2+)-dependent glutamate release.