Fig. 2: Shared and specific alterations in putaminal amino acid concentrations of untreated and L-DOPA-treated MPTP-intoxicated monkeys relative to controls.

The Venn diagram illustrates the overlap between amino acids significantly upregulated in untreated MPTP-intoxicated monkeys compared with controls (green) and those upregulated in MPTP + L-DOPA-treated monkeys compared with controls (purple). Five amino acids — serine, GABA, phenylalanine, valine, and isoleucine — were commonly upregulated in both untreated and L-DOPA-treated MPTP-intoxicated monkeys relative to controls. Leucine, aspartate, and glutamate were selectively increased in MPTP-intoxicated monkeys, whereas glycine, citrulline, and threonine were selectively increased in the MPTP + L-DOPA–treated group. Ctrl control, MPTP 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.