Inflammation, neurotoxins and psychiatric disorders.

Although immune reactions are necessary to defend against danger signals, the mediator molecules such as cytokines can be detrimental to the organism if the exposure is longer than necessary or in certain abnormal concentrations. The neuroprotection and neurotoxicity induced by the interaction between certain cytokines and the metabolites from tryptophan catabolism, the neuroactive kynurenines, which is partly influenced by corticosteroid action plays an important role in several neurotransmissions such as serotonergic, dopaminergic and glutamatergic transmissions and receptor functions such as N-methyl-D-aspartate receptor or α7-nicotinic-acetylcholine receptor. While the molecules in normal concentrations are essential to the normal glial-neuronal interaction, any changes that induce imbalance in the network between those molecules could disturb the interaction. The role of this network in major psychiatric disorders such as depression, bipolar disorder and schizophrenia and future therapeutic roles are discussed in this manuscript.