Effects of ascorbate in microdialysis perfusion medium on the extracellular basal concentration of glutamate in rat's striatum

There are many evidences suggest that ascorbate in the extracellular space can affect glutamate concentration in the rat's brain. In this report, we s tudied how ascorbate in microdialysis perfusion medium affected glutamate l evel at the striatum in freely-moving rats. Three perfusion mediums were us ed: 0, 250, and 400 mu M of ascorbate in perfusion medium. The extracellula r basal concentrations of glutamate were determined to be 1.29 +/- 0.52 mu M for the no ascorbate group, 0.86 +/- 0.35 mu M for the low ascorbate grou p and 4.76 +/- 1.48 mu M for the high ascorbate group. By using 400 mu M of ascorbate in a perfusion medium, we found that the extracellular basal con centration of glutamate significantly increased and its in vivo recovery si gnificantly decreased. This indicated that ascorbate concentration in a per fusion medium was important and must be carefully considered while using mi crodialysis technique to monitor glutamate concentration in vivo. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.