Objective:To investigate the arterial baroreflex (ABR)-associated mechanism of losartan in protection of acute cerebral ischemia injury in spontaneously hypertensive rats (SHRs).Methods:Losartan (10 mg·kg-1·d-1) were administered i.g. to SHRs for 2 weeks,and the hemodynamic parameters and the baroreflex sensitivity (BRS) was determined.Then the rats were subjected to middle cerebral arterial (MCA) occlusion to establish acute cerebreal ischemia.The brain samples were obtained,sectioned and stained 24 h later; the infarction area of the brain was measured.Losartan and angiotensinⅡ (AngⅡ,100 pmol) were also microinjected into the nucleus of solitary tract (NTS) of rats,and the hemodynamic parameters and BRS were determined 24 h later.Then the rats were subjected to MCA occlusion to establish acute cerebral ischemia injury.The brain infarction area was measured 24 h after operation.Results:Compared to control rats,intragastric administration of losartan improved the ABR function and significantly decreased the infarction area (P<0.05).NTS microinjection of AngⅡ obviously increased the blood pressure,and decreased BRS value of rats.NTS microinjection of losartan did not change the blood pressure,and significantly improved the ABR function(P<0.05) and alleviated cerebral infarction injury(P<0.05).Conclusion:Losartan can improve the sensitivity of ABR and prevent acute cerebral infarction; NTS might be the target of losartan.