| Background: Epilepsy is one of the most familiar neural diseases that has severely affect the patients'health and quality of life. The existing antiepileptic drugs have limited effects on this disease by some mechanisms, such as, Na+ ionic channels, Ca2+ ionic channels and the receptors of GABAA, et al. There are still twenty-five percent patients can not be controlled effectively in clinical, so the search for new antiepileptic drugs is urgent. Ginkgo biloba extract (GBE) is a natural remedy that has been used broadly in clinical and has few side effects. It may affect various targets and may prevent and treat epilepsy more effectively. Object: In order to evaluate the effects of GBE on epilepsy and discuss the possible mechanism, we employed lithium-pilocarpine seizure(LPS) rat model to investigate the effects of GBE on behaviors, electroencephalogram(EEG) and the neurons and the immunoreactivity of microglias in hippocampus formation of LPS rats through pre-treatment and post-treatment administion modes. We expect to put forward a more safe and effective drug for the prevention and the treatment of epilepsy and provide experimental proof and guidance for the application of GBE preparation to the prevention and the treatment of clinical epilepsy. Method: We selected healthy male adult Sprague-Dawley (SD) rats as research objects. All drugs were administered intraperitoneally. One hundred and twenty rats were divided into five groups randomly: normal saline control group (n=6), GBE group (n=6), LPS group (30mg/kg,i.p.)(n=36), GBE pre-treatment group(100mg/kg,i.p.)(n=36), GBE post-treatment group (n=36), GBE was administered intraperitoneally an hour before pilocarpine and thirty minutes after pilocarpine. The research time was selected as three hours and one, three, seven, fourteen, sixty days after the intraperitoneal injection of pilocarpine. The latter three groups were divided into six subgroups. The praxiologial changes of rats were observed after intraperitoneal administration each day. (EEG) was recorded before the rats were sacrificed. The research sites were CA1, CA3 and the hilus of dentate gyrus of hippocampus. HE-stained and GSI-B4 (a marker of microglia) immunohistochemistry was used. Results: 1. Behaviors: normal saline control group and GBE group were all normal; The rate of seizure stage ≥4 of LPS group, GBE pre-treatment group and GBE post-treatment group was 91.67%,5.56% and 86.11% respectively;The mortality of LPS group, GBE pre-treatment group and GBE post-treatment group was 10%,0 and 7.69% respectively. The 4 stage latency of LPS group, GBE pre-treatment group and GBE post-treatment group was 30.38 ±12.01min ,62~128min and 30.75 ±12.92min respectively. There were significant differences in the rate of seizure stage ≥4 and seizure stage between GBE pre-treatment group and LPS group . The effective rate of GBE pre-treatment group and GBE post-treatment administration against LPS group was 94.44% and 35.48% respectively. 2. EEG: The EEG of normal saline control group and GBE group was normal. The frequency was increased on the EEG of LPS group. And therewere multiple spikes waves discharges or paroxysmal and continual spikes clusters discharges on the EEG of LPS group. There was only increasing frequency but no spikes waves discharges on the EEG of pre-treatment group. The EEG of post-treatment group is similar to that of LPS group. 3. Pathomorhology (1) HE staining: Compared with normal saline control group and GBE group, the number of the neurons in CA1,CA3 and the hilus of dentate gyrus of hippocampus decreased significantly at 14d and 60d , accompanying the microglia activation. Compared with LPS group, the loss of the neurons and the microglia activation lightened significantly in the GBE pre-treatment group. But there was no difference between GBE post-treatment group and LPS group. (2) GSI-B4 immunohistochemistry staining: Compared with normal saline control group and GBE group, the number of the GSI-B4-IR positive microglia in CA1, CA3 and the hilus of dentate gyrus...
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