TNF and major depressive disorder: In addition to exhibiting the core behavioral phenotypes of rat depression models, rats overexpressing MKP-1 in the hippocampus showed elevated expression levels of the inflammatory mediators [IL]-6 (t(10) = -5.490, P = 0.000) and [TNF]-ɑ (t(10) = -5.630, P = 0.000) but reduced p-ERK/ERK (t(10) = 3.648, P = 0.012), p-p38/p38 (t = 10.016, P = 0.000), and p-JNK/JNK (t(10) = 9.634, P = 0.000) as measured by Western blotting (Fig. 2D, E).