OBJECTIVE:To study the effects of Buyang huanwu decoction on the contents of CD40 and CD40L in the serum of rats with cerebral ischemia. METHODS:Rats were randomized into a sham-operation(normal saline)group,a model(normal saline)group,a positive control [6.75 mg/(kg·d)clopidogrel hydrogen sulfate] group and Buyang huanwu decoction high-dose and low-dose [26 and 6.5 g/(kg·d)] groups,with 20 rats in each group. Suture occlusion of middle cerebral artery was used to establish the rat models of focal cerebral ischemia,which were given drugs ig on the 2nd day after the operation and for 14 consecutive days. Then pathological changes in the cerebral tissues of all groups of rats were observed and the contents of CD40 and CD40L in the serum thereof were detected by euzyme-linked immunosorbent assay. RESULTS:The rats in the model group demonstrated isch-emia-like pathological change in the cerebral tissue on the side of lesion. The ischemia-like cerebral tissue on the side of lesion in the positive control group and Buyang huanwu decoction high-dose group were improved compared to the model group. The patho-logical change in the cerebral tissue on the side of lesion in Buyang huanwu decoction low-dose group was similar to that in the model group. The contents of CD40 and CD40L in the serum of rats in the model group were higher than in the sham-operation group. The content of CD40L in the serum of rats in positive control group and Buyang huanwu decoction high-dose group were lower than the model group. There were statistical differences(P<0.01 or P<0.05). Except as described above,no other statistical-ly significant differences (P>0.05) were noted. CONCLUSIONS:Buyang huanwu decoction can improve brain cell morphology and reduce cerebral ischemic tissue injury in model rat with cerebral ischemia by a mechanism which may be related to decreasing the content of CD40L.