TNF and major depressive disorder: The immobility time of the tail suspension test and forced swimming test (as a proxy of depression-like behavior) was positively correlated with the levels of proinflammatory cytokines (IL-1β, IL-6, and TNF-α) and was negatively correlated with the levels of synaptic plasticity-associated proteins (BDNF, TrkB, PSD-95, and SYN), as shown in Table 1.