Effects of electroacupuncture on astrocytes in the marginal zone of focal cerebral ischemia in rats

BACKGROUND:Astrocytes react sensitively to cerebral ischemia,causing reactive proliferation and activation,which may contribute to their effect in protecting or injuring neuronal regeneration. Whether acupuncture,as a treatment for cerebral ischemia,regulates the activated state of astrocytes has become a focus of recent investigations. OBJECTIVE:To observe the effects of electroacupuncture(EA) on ultrastructure changes and reactive proliferation of astrocytes in the marginal zone of focal cerebral ischemia in rats. DESIGN,TIME AND SETTING:Randomized,controlled animal study.This study was performed at the Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine between December 2007 and July 2008. MATERIALS:A total of 90 male Wistar rats were randomly divided into sham operated,model and EA groups.Each group was subdivided into 1 hour,1,3,7,and 21 days post-cerebral ischemia groups,with six animals for each time point.Rabbit anti-rat glial fibrillary acidic protein (GFAP) and goat anti-rabbit IgG/tetramethylrhodamine isothiocyanate were provided by Beijing Biosynthesis Biotechnology.The G-6805 electric acupuncture apparatus was provided by Shanghai Huayi. METHODS:Heat-coagulation-induced occlusion of the middle cerebral artery was performed to establish a model of focal cerebral ischemia,in the model and EA groups.Middle cerebral arteries were exposed without occlusion in sham operated group.EA was applied immediately after surgery in the EA group,4/20 Hz,2.0-3.0 V,1-3 mA,to Baihui(GV 20) and Dazhui(GV 14),for 30 minutes.The treatment was performed once a day.The sham operated and model groups did not receive acupuncture. MAIN OUTCOME MEASURES:In the marginal zone of focal cerebral ischemia in rats at different time points after intervention,the ultrastructure changes of astrocytes were observed by using transmission electronic microscopy.GFAP expression in astrocytes was also measured by laser confocal scanning microscopy. RESULTS:Cell swelling and rapid proliferation of astrocytes were observed following cerebral ischemia.In comparison to the model group,the degree of swelling of astrocytes was significantly decreased in the EA group.Compared with the sham operated group at hour 1 post-surgery,there was no significant difference in the expression of average fluorescence intensity of GFAP between the EA and model groups(P>0.05),while the expression of GFAP in both the EA and model groups increased significantly at days 1,3,7 and 21 post-surgery(P<0.01).The expression of GFAP in EA group was also significantly lower than in the model group(P<0.01,P<0.05). CONCLUSION:Ultrastructural changes and reactive proliferation of astrocytes appear in the marginal zone of focal cerebral ischemia in rats.EA can relieve the degree of swelling of astrocytes and inhibit GFAP overexpression by activated astrocytes.These effects may be related to its ability to regulate the activated state of astrocytes.