N-Acetyl-aspartylglutamate (NAAG) in human cerebrospinal fluid: Determination by high performance liquid chromatography, and influence of biological variables.

NAAG is one of the neuropeptides found in highest concentrations in the CNS. The presence of micromolar concentrations of NAAG in human CSF was demonstrated by using two different and complementary analytical approaches: 1) isocratic separation of endogenous NAAG by reverse-phase high performance liquid chromatography (HPLC) with dual wavelength detection and 2) derivatization of endogenous NAAG with acidic methanol and subsequent HPLC analysis of the derivative NAAG-trimethyl ester. The NAAG concentration was between 0.44µmol/l and 7.16µmol/l (mean of 2.19 ± 1.53µmol/l) in CSF samples from forty neuropsychiatric patients. Endogenous NAAG or [(3)H]NAAG added to CSF samples were not significantly degraded when the CSF was incubated at 37°C during one hour, suggesting that the peptide is a highly stable metabolite in the subarachnoid space. In addition, evidence is provided that NAAG does not present a concentration gradient along the lower subarachnoid space.