Abstract: Objective： To investigate the expression of activin A (ACT-A) in brain tissues of neonatal rats with hypoxia and ischemia (HI). Methods： The left common carotid arteries of neonatal rats at 7 days in the hypoxic ischemic brain damage（HIBD） group were ligated, and then they were subjected to 8% oxygen for 2 hours. Expressions and origins of ACT-A were determined by immunohistochemical and histopathologic methods. Results： Positive ACT-A cells were found in the left cingulum cortical area 1h after HI, and obviously increased compared with those in the control group and in the contralateral area ［(2.50±1.51) vs (1.13±0.64)，and (2.50±1.51) vs (1.00±0.76)， P<0.05］. Expression of ACT A reached a peak at 10 hours after HI. Large amounts of positive ACT A cells were found in the left cingulum cortical， corpus striatum， dentate gyrus, and were obviously increased compared with that in the control group ［(19.75±2.19) vs (1.25±0.71)， P<0.01］ and in the contralateral area ［(19.75±2.19) vs (1.00±0.76)， P<0.01］. Overexpression of ACT-A was found till 72 hours after HI ［(12.75±3.62) vs (1.38±0.74)， and (12.75±3.62) vs (1.00±0.76)， P<0.05］. Conclusion： Hypoxiaischemia strongly induces the expression of ACT-A. This suggests that ACT-A may play an important role in the pathogenic process of HIBD in newborn rats.

Key words: Rats, Wistar, Hypoxiaischemia, brain, Activin A