Objective: To investigate the effects of Yinaokang capsule (YC) on blood-brain barrier opening and expression of zonular occludens protein (ZO-1 protein) after thrombolysis therapy by recombinant tissue type plasminogen activator (rt-PA) in rats. Method: The rats were randomly divided into sham operation group

thrombolysis group

YC low dose group (1 g·kg-1daily for 3 d)

YC high dose group (3 g·kg-1daily for 3 d). Model of middle cerebral artery occlusion in rats was established by embolizing left middle cerebral artery with autologous blood clots. The permeability of the brain-blood barrier was observed with Evan's blue (EB) with spectrophotometer and the expression of ZO-1 protein was detected by Western blot. Result: Compared with the sham group

EB leakage in brain tissue was increased significantly and the expression of ZO-1 protein was decreased obviously in all other groups. Compared with the thrombolysis group

the EB leakage showed no difference in YC low dose group and increased in the high dose YC group; the expression of ZO-1 protein was increased significantly in both YC groups. Compared with the low dose YC group

the EB leakage in the high dose YC group was decreased

and the expression of ZO-1 protein in the high dose YC group was increased. Conclusion: YC could attenuate the breakdown of brain-blood barrier after thrombolysis therapy. Its mechanisms may be associated with up-regulated expression of ZO-1 protein.