Identification and determination of nucleosides in rat brain microdialysates by liquid chromatography/electrospray tandem mass spectrometry.

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed for the determination of brain basal nucleosides (inosine, guanosine and adenosine) in microdialysates from the striatum and cortex of freely moving rats. A microdialysis probe was surgically implanted into the striatum or cortex of individual rats and Ringer's solution was used as the perfusion medium at a flow rate of 0.3 or 0.5 microl/min. The samples were then analyzed off-line by LC/MS/MS experiments. The separation of inosine, guanosine and adenosine was carried out on a cyano column using a mobile phase of 10 mM ammonium acetate, 1% acetic acid and 8% methanol at a flow rate of 0.4 ml/min. Analytes were detected by electrospray ionization tandem mass spectrometry in the positive ion mode. The detection limit for inosine, guanosine and adenosine was 80, 80 and 40 pg on column, respectively. With this method, the intercellular basal inosine, guanosine and adenosine concentrations in striatum and cortex of rat were determined.