STAT3 and serum lipopolysaccharide activity: To further determine whether HA pretreatment regulated STAT3 activation and pro-MMP-9 expression in the hippocampus during endotoxemia-mediated acute sickness behavior and anxiety-like behavior, the expression levels of phosphorylated STAT3 (Tyr705) and pro-MMP-9 expression were evaluated by immunoblotting and gelatin zymography, respectively.