Amino acid patterns in schizophrenia: some new findings.

Blood concentrations of various amino acids were measured in schizophrenic patients and control subjects. Significantly higher blood concentrations of glycine, glutamate, and serine were found in the schizophrenic patients. Glycine was abnormally elevated in subjects with paranoid or undifferentiated schizophrenia, but not in disorganized patients. Since glutamate, glycine, and serine play a complex role in the regulation of N-methyl-D-aspartate (NMDA) receptors, which are important in the control of normal cognitive processes, we hypothesized that the elevated levels of these amino acids might disrupt the normal functioning of NMDA receptors and might be involved in the pathophysiology of schizophrenia.