TLR4 and migraine disorder: Researchers have shown that TLR4 signaling is involved in initiating and maintaining migraine-like behavior and nucleus caudalis neuronal activation in mice (Ramachandran et al., 2019) and that it could promote hyperalgesia by stimulating the production of proinflammatory cytokines and activating microglia in a rat model of migraine (Su et al., 2018).