Effects Of Estrogen And Chronic Brain Ischemia On 2VO-OVX Rats

Objective: To observe the effects of estrogen and chronic brain ischemia on the behavior tests , histopathology , the number of nitric oxide synthase(NOS) positive neurons in hippocampal CA1 area of rats after 2VO(bilateral common carotid occlusion) and OVX(ovariectomy). Furthermore, to study the effects of estrogen replacement on the rats after OVX. Gathering morphologic evidence of the neuro-protection effects of estrogen on the rat chronic brain ischemia.Methods: The animal models were established by 2VO(bilateral common carotid occlusion) and OVX(ovariectomy). 10 months old female Sprague-Dawley rats were randomly divided into 5 groups: A group , control group , with no treatments ; B group , sham-operation group , only bilateral common carotid and ovary were exposed , and boiled sesame 0.2ml/3d after operation were injected into abdominal cavity ; C group, 2VO ; D group, OVX+2VO, and were treated estrogen 0.2ml/3d correspondingly; E group, OVX+2VO, and were treated boiled sesame 0.2ml/3d correspondingly. After 9 weeks, all rats were studied in open field test and T maze test to detect the ability of memory and studying. Then all rats were killed and extracted the pieces of the hippocampus ,which were divided into 2 halves: the anterior half were freezed and sliced to stained by NADPH histochemical method; and the posterior were immersed into wax and sliced for HE staining. We also observed the ultrastructure changes of the neurons in hippocampal CA1 area of the rats of A and C group.Results: 1.It was showed by the behavior tests that the learning and memory abilities of the rats deduced after 2VO and OVX , especially inE group, the D group improved after estrogen treatment. 2.Morphological study demonstrated that the neurons were dead in different grades after 2VO by HE staining , the number of survival neurons of hippocampal CA1 area decreased, especially in E group. 3.Significant changes in neurons and the affiliated structure such as mitochondria were found at the electronic microscopic level. 4.The NADPH histochemical staining showed that the number of NOS positive neurons of hippocampal CA1 area of C, D and E group decreased after 2VO, compared with D group, the E group decreased more obviously.Conclusions: l.The abilities of learning and memory deduced; the number of survival neurons and NOS positive neurons of hippocampal CA1 area decreased; the change of neurons at ultrastructure level were found after 2VO. 2. The impairments were aggravated and the decreasing of NOS positive cells is more significant after OVX, but reversed by the estrogen replacement therapy.