TNF and major depressive disorder: Glial cells are considered a major source of cytokines and chemokines in the brain [122], and the activation of microglia in ACC, hippocampus, prefrontal cortex and other brain regions associated with pain information processing contributes to pain aversion [123], memory deficits [124], anxiety and depression [124] and may be associated with overexpression of TNF-α [20,125].