A simple LC-MS/MS method for quantitative analysis of underivatized neurotransmitters in rats urine: assay development, validation and application in the CUMS rat model.

Many amino acid neurotransmitters in urine are associated with chronic stress as well as major depressive disorders. To better understand depression, an analytical LC-MS/MS method for the simultaneous determination of 11 underivatized neurotransmitters (4-aminohippurate, 5-HIAA, glutamate, glutamine, hippurate, pimelate, proline, tryptophan, tyramine, tyrosine and valine) in a single analytical run was developed. The advantage of this method is the simple preparation in that there is no need to deconjugate the urine samples. The quantification range was 25-12,800 ng mL(-1) with >85.8% recovery for all analytes. The nocturnal urine concentrations of the 11 neurotransmitters in chronic unpredictable mild stress (CUMS) model rats and control group (n = 12) were analyzed. A series of significant changes in urinary excretion of neurotransmitters could be detected: the urinary glutamate, glutamine, hippurate and tyramine concentrations were significantly lower in the CUMS group. In addition, the urinary concentrations of tryptophan as well as tyrosine were significantly higher in chronically stressed rats. This method allows the assessment of the neurotransmitters associated with CUMS in rat urine in a single analytical run, making it suitable for implementation as a routine technique in depression research.