RELEASE OF GLUTAMATE FROM STRIATUM OF FREELY MOVING RATS BY PROS-METHYLIMIDAZOLEACETIC ACID

The effect of pros-methylimidazoleacetic acid (p-MIAA) was measured on the release of glutamate and aspartate from cerebral cortex, hippocam pus, and striatum of freely moving rats, and on the uptake of C-14 by striatal slices incubated in the presence of L-[C-14]glutamate. Twenty -four hours after implantation of a dialysis fiber, striatum, hippocam pus, or cerebral cortex spontaneously released both glutamate and aspa rtate in the micromolar range. p-MIAA(1 mu M to 1 mM), added to the di alysis perfusate, elicited a concentration-dependent increase of gluta mate 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-MIA A effect was not mimicked by its isomer tele-methyl-imidazoleacetic ac id. p-MIAA did not influence the uptake of glutamate by striatal slice s. The glutamate-releasing action of p-MIAA may affect striatal functi on and explain the positive correlation between levels of p-MIAA in CS F and the severity of Parkinson's disease.