TLR4 and Anxiety: Moreover, the study indicated that chronic methamphetamines (METH) induced anxiety-like behavior in rats, at least in part, by activating the immune Toll-like receptor 4 (TLR4) signaling pathway, which leads to the upregulation of the expression of several inflammatory agents, such as NF-κB and α-actin in the hippocampus (Wang et al., 2019; Rezaeian et al., 2020).