Abstract:

Objective   To investigate the effects of progesterone on early brain injury in rats after subarachnoid hemorrhage (SAH) and the possible mechanism involved. Methods   Forty-eight adult male SD rats were randomly divided into three groups: the Sham operation group, the SAH group and the progesterone group (PG). An SAH model was established by injecting autologous blood into the cisterna magna. After 48h, the morphology of hippocampal neural cells was examined in sections stained with hematoxylin and eosinfor all groups. Neuronal apoptosis in the hippocampus was assessed by TUNEL. Expression of Bcl-2 (an anti-apoptotic protein) and Bax (a pro-apoptotic protein) was investigated with immunohistochemistry. Results   Compared with the SAH group, the PG group exhibited significantly low rates of apoptosis in the hippocampus neurons (P<0.05), with expression of Bcl-2  up-regulated (P<0.05) and Bax down-regulated (P<0.05). Conclusion   Progesterone apparently enhances Bcl-2 expression and inhibits  Bax expression (thus increasing the Bcl-2/Bax ratio),  leading to low apoptosis rates in hippocampus neuronal cells. This is likely responsible for the observed protective effects of progesterone on the EBI after SAH.

Key words: Subarachnoid hemorrhage; Early brain injury; Progesterone; Apoptosis; Bcl-2; Bax