Abstract: ObjectiveTo explore possible mechanism of antipyretic effect of baicalin in rats with yeast-induced fever.MethodsRat pyrexia model was established via subcutaneous injection of yeast(2 g·kg ^-1);32 pyrexia model rats were then equally divided into a model group and low-,medium-,and high-dose groups with the administration of baicalin via gastric gavage at dosages of 40,80,and 160 mg/kg;a control group(8 rats) was set up via gastric gavage of 10 mL/kg saline and subcutaneous injection of phosphate buffered saline solution(PBS).The effect of baicalin on changes in body temperature of the rats was observed.The expressions of interleukin-1β(IL-1β)and tumor necrosis factor-α(TNF-α)were determined with enzyme-linked immunosorbent assay(ELISA).The expression of Toll-like receptor 4(TLR4)mRNA was determined with reveres transcriptase(RT)-PCR.The expressions of TLR4,P65,inhibitor k binding α(IκBα) protein were determined with Western blot.ResultsCompared with the control rats, the body temperature(40.6±0.4 ℃) of model rats 8 hours after yeast injection increased significantly(P<0.01);serum IL-1β(263.55±32.86 pg/L) and TNF-α(54.66±8.60 ng/L)increased significantly(P<0.05);the protein expressions of TLR4 and p65 in brain tissue increased significantly and the protein expression of IκBα decreased significantly(P<0.01).For the rats in medium- and high-dose group,the body temperature(38.2±0.5 and 38.0±0.3℃)was significantly decreased(P<0.05);the serum IL-1β (225.32±11.88 and 205.18±41.36 pg/L)and TNF-α(35.20±7.12 and 25.04±9.27 ng/L) decreased significantly(P <0.05);and the protein expression of TLR4 and p65 decreased,IκBαprotein increased significantly(P<0.01).ConclusionBaicalin has obvious antipyretic effect and the mechanism of the effect may be related to the inhibition of TLR4/nuclear factor-κB(NF-κB).