Release of Glutamate from Striatum of Freely Moving Rats by pros-Methylimidazoleacetic Acid

Abstract: The effect of pros -methylimidazoleacetic acid (p-MIAA) was measured on the release of glutamate and aspartate from cerebral cortex, hippocampus, and striatum of freely moving rats, and on the uptake of ¹⁴C by striatal slices incubated in the presence of l -¹⁴C]-glutamate. Twenty-four hours after implantation of a dialysis fiber, striatum, hippocampus, or cerebral cortex spontaneously released both glutamate and aspartate in the micromolar range. p-MIAA (1 µ M to 1 m M ), added to the dialysis perfusate, elicited a concentration-dependent increase of glutamate release from striatum with a maximal increase of about threefold. This effect did not occur in hippocampus or cortex. In none of these regions did p-MIAA increase aspartate release significantly. The p-MIAA effect was not mimicked by its isomer tele -methylimidazoleacetic acid. p-MIAA did not influence the uptake of glutamate by striatal slices. The glutamate-releasing action of p-MIAA may affect striatal function and explain the positive correlation between levels of p-MIAA in CSF and the severity of Parkinson's disease.