Abstract: Antipyretic effect and mechanisms of  Forsythia suspensa extract and forsythia oil on rats with high fever induced by yeast were investigated in the study. Rat model of yeast-induced fever was established by subcutaneous injections of yeast. After the basal body temperature was measured, the rats were randomly divided into four groups:control group,model group, Forsythia extract group (25 crude drug g/kg) andforsythia oil group (26.7 crude g/kg). Then the body temperature and the concentration of prostaglandin E2 (PGE-2) and cyclic adenosine monophosphate (cAMP) in the hypothalamus cerebrospinal fluid of rats were detected dynamically two hours after dosing. The result showed that  F.suspensa extract and forsythia oilcan significantly decrease the temperature(P<0.01 or  P <0.05)as well as hypothalamus cAMP content (P<0.01) in yeast-induced fever rats.In addition, F.suspensa  extract also obviously decreased hypothalamus PGE-2 content (P<0.01). F.suspensa extract can down-regulate cAMP and PGE-2 in hypothalamus. And forsythia oil down-regulate cAMP in hypothalamus. Both can be used as symptomatic treatment for clinical fever.

Key words: Forsythia suspensa extract, forsythia oil, antipyretic mechanism, cAMP, PGE-2