We also used lipopolysaccharide (LPS), an agonist of TLR4, in an in vitro model of macrophage IL-1β and TNF release (19) and in an in vivo paradigm of “sickness behavior,” measuring inflammation-induced signs of anxiety, hypolocomotion, and suppressed exploration in mice (21, 22, 34, 35). Here, TNF is linked to Anxiety.