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 studied how ascorbate in microdialysis perfusion medium affected glutamate level at the striatum in freely-moving rats. Three perfusion mediums were used: 0, 250, and 400 microM of ascorbate in perfusion medium. The extracellular basal concentrations of glutamate were determined to be 1.29+/-0.52 microM for the no ascorbate group, 0.86+/-0.35 microM for the low ascorbate group and 4.76+/-1.48 microM for the high ascorbate group. By using 400 microM of ascorbate in a perfusion medium, we found that the extracellular basal concentration of glutamate significantly increased and its in vivo recovery significantly decreased. This indicated that ascorbate concentration in a perfusion medium was important and must be carefully considered while using microdialysis technique to monitor glutamate concentration in vivo.