| Background:Epilepsy, one of the most common neurological disorders , its pathophysiological alterations are abnormal discharges originating simultaneously in partial or both hemispheres of the brain. Despite having newly approved antiepileptic drugs(AEDs), about 20%～30% of patients are refractory to the treatment. The mechanism of refractory epilepsy(RE) is not clear. The recent finding is that there are many kinds of multidrug transporters reside in the blood-brain barrier(BBB), which is correlation to the multidrug resistance of epilepsy. multidrug transporters are some protein that associated with drugs and carting drugs from cells. include ATP-bingding cassette (ABC) super-family, suah as P-glycoprotein(P-gp),multidrug resistance associated p-rotein(MRP),breast cancer resistant protein(BCRP), brain multidrug resistance protein(BMDRP),and Ral-interacting protein76(RL-IP76) which is belongs to Ras super-family. They act as drug efflux pump and actively make drugs out of the brain to protect the brain tissue in physiological condition. So the expression of multidrug transporters are direct ratio to the depression of drug concentration in brain. P-gp is recognized as the earliest multidrug transporters expressed in brain. it is encoded by multidrug resistant gene(MDR). P-gp is over expressed in the pathological circumstance, such as epileptic degree, time course and antiepile- ptic drugs, limiting penetration of antiepileptic drugs into the brain,lowering the concentration of drugs in the vicinity of epileptogenic focus,this mechanisms maybe involved in the drug resistance in refractory epilepsy. So the way to improve the prognosis of drug-resistant epilepsy is to against the over-expression of P-gp , avoid its efflux function and instrengthen the role of antiepileptic drugs, There are lot of P-gp inhibitor drugs have been gradually confirmed , including calcium channel blockers, hormones, protein kinase C (PKC) inhibitors, immuno- suppressive agents, antibiotics, surfactants. But these study were concentrated in effecting the functional of P-gp. So we established a chronic epileptic rat model, P-glycoprotein inhibitors united conventional antiepileptic drugs therapeutically, we can study the effect of p-glycop- rotein inhibitor on the expression of P-gp in the brain with refractory epilepsy, examine the effect of P-glycoprotein inhibitor. We hope to find a new strategy for refractory epileptic patients.Objective To establish rat model of chronic epilepsy induced by the Lithium- pilocar pine, investigate the effect of multidrug resistance gene protein inhibitor verapamil on the electroencephalography(EEG), the frequency and degree of spontaneous recurrent seizures (SRS) and the expression of P-glycoprotein (P-gp) of rats with refractory epilepsy.Method (1)To establish rat model of chronic epilepsy: install the cortical electrode, and induce the status epilepticus(SE) by the Lithium- pilocarpine after retrieve of two week. The rat model of refractory epilepsy could be estbalihsed successfully when the rats were survival, had a good condition after SE, and developed into SRS after about 2 weeks. (2)the rats in the successful model, after the selection of drug resistance, were divided into the normal sodium group, pilocarpine group, carbamazepine group, low-dose verapamil group and high-dose verapamil group randomly, and were gaven corresponding drug by intragastric administration, we can record the EEG and observe the frequency and degree of SRS, the expression of P-gp was investigated in cortex and hippocampus in rat of every group by immunohistochemisty staining, Complete the statistics by the ratio of area of object to total area of image (Object/Total).Results (1) During the establishing, forty-four rats were induced into SE successfully beside the six rats which were were divided into the normal sodium group, there are thirty-three rats were survival and have a good condition after SE, thirty-two developed into SRS among them, the achievement ratio of establishing is 72.3%, Automatism and complex partial epilepsy exhibition were seen after pilocarpine injection and developed into tonic-clonic seizure subsequently. Atfer lh,the persistent status epeilpetiucs(SE) was putdown by intramuscularly injecting diazepam.The rat developed into silenet period after 2 days and then into spontaneous recurrnet seizures (SRS) after 2 weeks. (2) We coud not found obviously differnce about seizure frequency and degree between pilocarpine group and carbamazepine group(P>0.05), while the two verapamil groups have a evident decrease in the frequency(P<0.05), and the seizure degree of two verapamil groups is lighter (P<0.05)than the forward two sets, but there is no obviously differnce between low-dose verapamil group and high-dose verapamil group(P>0.05). EEG: intervallic polyspike discharge with high potential was seen on a relatively normal background in pilocarpine group, carbamazepine group have paroxysmal spikes with lower wave than pilocarpine group, single epileptic electric discharge in a low degree appear in the two verapamil groups. (3) The expression of P-gp in hippocampus is more than cortex(P<0.05). Among the five group, compared with control group,P-gp was relatively enhanced in the other four groups. and there is signifieant dieffrence among pilocarpine group, carbamazepine group and two verapamil groups (P <0.05), but there is not signifieant dieffrence in low-dose verapamil group and high-dose verapamil group (P>0.05).Conclusion (1)The model induced by pilocarpine in rats can replicate features of complex partial seizure in human temporal epilepsy, it may be a ideal animal model for studying refractory epilepsy (RE). (2)A markedly suppression of epileptic electric discharge and seizure frequency was recorded after consociation use of CBZ and verapamil(;3)The expression of P-gp was also obviously degraded after using verapamil.
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