Determination of kynurenic acid levels in rat brain microdialysis samples and changes in kynurenic acid levels induced by N ‐acetylaspartic acid

The levels of kynurenic acid, an endogenous antagonist of α 7 nicotinic acetylcholine and N ‐methyl‐ D ‐aspartate receptors, were measured in microdialysis samples obtained from the prefrontal cortices of rats using column‐switching high‐performance liquid chromatography with fluorescence detection. When the perfusate was constantly infused at a rate of 1.0  μ /min, the in vitro recovery of kynurenic acid through the dialysis membrane was approximately 20.4%, and the precision was within 1.31%. Endogenous kynurenic acid in the microdialysis sample was clearly detected using column‐switching high‐performance liquid chromatography. As an application study, N ‐acetyl‐ L ‐aspartic acid, an endogenous metabolite and precursor of N ‐acetyl‐ L ‐aspartyl‐ L ‐glutamic acid, which is an agonist of metabotropic glutamate receptors, was infused for 120 min through the microdialysis probe. The kynurenic acid level significantly increased during the infusion of N ‐acetyl‐ L ‐aspartic acid, suggesting that kynurenic acid might have some association with N ‐acetyl‐ L ‐aspartic acid in vivo . Copyright © 2009 John Wiley & Sons, Ltd.