Figure 1.
Potential neurotoxic consequences of kynurenine pathway activation resulting from peripheral induction of indoleamine 2,3-dioxygenase (IDO). Asterisks represent pathway metabolites that cross the blood-brain barrier. TRP, tryptophan; KYN, kynurenine; IFN, interferon; IL, interleukin; 3-HK, 3-hydroxykynurenine; 3-HAA, 3-hydroxyanthranilic acid; QUIN, quinolinic acid; KA, kynurenic acid; NMDA, N-methyl- D-aspartate; GABA, γ-aminobutyric acid