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Figure 1 | BMC Psychiatry

Figure 1

From: Etiological classification of depression based on the enzymes of tryptophan metabolism

Figure 1

Impaired glial-neuronal network. Impaired glial-neuronal network expressed by peripheral and central key enzymes of tryptophan metabolism. Hypofunctional peripheral 5-HTP cells (reflecting TPH1 dysfunction) cause a reduction in 5-HTP levels that lead to a reduction in brain 5-HT levels. In major depression, neurotoxic kynurenine metabolites (e.g., 3-HK and QUIN derived from 3-HK) and/or TPH1 dysfunction combined with compensatory TPH2 activation, may induce astrocytic and neuronal apoptosis.

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