SERUM LEVELS OF EXCITATORY AMINO-ACIDS, SERINE, GLYCINE, HISTIDINE, THREONINE, TAURINE, ALANINE AND ARGININE IN TREATMENT-RESISTANT DEPRESSION - MODULATION BY TREATMENT WITH ANTIDEPRESSANTS AND PREDICTION OF CLINICAL RESPONSIVITY

Previous research has revealed that major depression is accompanied by disorders in excitatory amino acids, e.g. glutamate and aspartate, an d alterations in serum levels of other amino acids, e.g. serine, glyci ne and taurine. The aim of the present study was to examine serum leve ls of aspartate, asparagine, glutamate, glutamine, serine, glycine, th reonine, histidine, alanine, taurine and arginine in major depression patients with treatment-resistant depression (TRD). No significant dif ferences in the serum concentrations of any of the above amino acids c ould be found between patients with and without TRD and normal control s. Non-responders to treatment with antidepressants during a period of 5 weeks were characterized by significantly lower serum levels of asp artate, asparagine, serine, threonine and taurine. A 5-week period of treatment with antidepressants significantly reduced the serum levels of aspartate, glutamate and taurine, and significantly increased the s erum concentrations of glutamine. The results suggest that alterations in serum levels of aspartate, asparagine, serine, threonine and tauri ne may predict the subsequent response to treatment with antidepressan ts, and that the latter may modulate serum levels of excitatory amino acids and taurine.