Abstract: Objective To investigate the role of Bcl-2 in the cytoprotective effect of thyroid hormone against hippocampal cell
apoptosis in rats with chronic cerebral ischemia. Methods Fifty adult male SD rats were randomized into sham-operated
group, 2-vessel occlusion (2VO) group and triiodothyronine (T3) treatment group. At 7 and 14 days after the operation, the
tissue structure of the CA1 region was observed with Nissl staining, and TUNEL staining was used to determine the apoptosis
index (AI) in the dentate gyrus; Western blotting was performed to detect the expression level of Bcl-2 in the hippocampus.
Results In the 2VO group, the CA1 region of the hippocampus showed obvious structural damages with reduced number of
neurons, and these changes were significantly improved in T3 treatment group. At 7 days after the operation, no significant
difference was found in AI between the sham-operated group (17.714±2.553), 2VO group (20.868±2.090) and T3 group (20.365±
1.055) (P=0.060); the expression level of Bcl-2 was higher in T3 group than in 2VO group. On day 14, AI was 66.532±3.249 in
2VO group, significantly higher than that in T3 treatment group (56.153±4.556, P=0.001); Bcl-2 expression was the highest in T3
group and the lowest in 2VO group. Conclusion Thyroid hormone can reduce cell apoptosis in the hippocampus of rats with
chronic cerebral ischemia possibly by up-regulating the expression of Bcl-2.