Analysis of human cerebrospinal fluid monoamines and their cofactors by HPLC

The presence of monoamines and their cofactors (the pterins and vitamin B-6 (pyridoxal phosphate (PLPPLPPLP))) in human cerebrospinal fluid (CSCSF) can be used as indicators of the biosynthesis and turnover of dopamine and serotonin in the brain. In addition, abnormalities in the CSCSF levels of these molecules are associated with various neurological diseases, including genetic diseases leading to dopamine and serotonin deficiency. Here, we provide a set of quantitative high-performance liquid-chromatography (HPLCPLCPLC) approaches to determine CSCSF levels of monoamines and their cofactors. This protocol describes step-by-step procedures for CSCSF sample preparation for the analysis of different molecules, HPLCPLCPLC calibration and analysis, and data quantification and interpretation. Unlike plasma/tissue/blood samples, CSCSF requires minimal sample preparation: in this protocol, only the analysis of PLPPLPPLP requires mixing with trichloroacetic acid to release the protein-bound vitamin, centrifugation, and mixing of the supernatant with phosphate buffer and sodium cyanide for derivatization in alkaline conditions. Monoamines are analyzed by HPLCPLCPLC with coulometric electrochemical detection (ED), pterins are analyzed by HPLCPLCPLC with coupled coulometric electrochemical and fluorescence detection, and PLPPLPPLP is analyzed by HPLCPLCPLC with fluorescence detection. The quantification of all compounds is achieved by external calibration procedures, and internal quality control and standards are analyzed in each run. We anticipate that investigation of dopamine and serotonin disturbances will be facilitated by measurements of these compounds in human CSCSF and other biological samples. The estimated time for the different procedures primarily depends on the electrochemical detector stabilization. Overnight stabilization of this detector is advised, and, after that step, preanalytical equilibration rarely exceeds 3 h.