Effect Of Low-frequency Repetitive Transcranial Magnetic Stimulation On The Expression Of PGP, MRP1, MVP In The Hippocampal Region Of Lithium-pilocarpine Induced Chronic Epilepsy Rats

Objective: based on the lithium-pilocarpine induced chronic epilepsy ratmode, the impact of low-frequency repetitive transcranial magneticstimulation(rTMS) on behavior of these chronic epilepsy rats and expressionof three multidrug resistance-associated protein drugs: P-glycoprotein,multidrug-resistant1, Major Vault Protein in the rat hippocampus CA3regionwere investigated, aiming to explore the anti-epileptic mechanisms of rTMSand provide some evidence for its further use in the treatment of RE.Method:8~10-week old male Sprague-Dawley (SD) rats were adoptedin this study. All rats were first given an intraperitoneal injection of Lithium,then followed by repeated low-dose pilocarpin to make epileptic seizuremodel. After recovery for several days, the video and electroencephalogram(EEG)were used to monitor the rats’behavior and epileptiform discharges,respectively. Those with seizure attack in vedio and epileptiform dischargeson EEG were defined as chronic epilepsy rats. The chronic epilepsy rats wererandomly divided into stimulus group and non-stimulus group (including themodel group and the sham stimulation group). Meanwhile, a control groupwas also set up (intraperitoneal injection of saline). The rats in stimulus groupwere treated with rTMS, which was administered with5trains of100pulsesand an intensity of40%MT at0.5HZ on14consecutive days. The rats insham group and model group were treated with sham rTMS and nothing else, respectively. The number of seizures during the treatment in each group wasrecorded. The rats were killed and perfused after corresponding treatme-nt onthe first day,7th day and14thday. Immunohistochemical staining was used totest the expression of PGP, MRP1, MVP in the rat hippocampal CA3region.Result:1. We successfully established a lithium chloride–pilocarpinechronic epilepsy rat model based on the behavior and EEG: after2-5dose of10mg/kg pilocarpine induction, most rats developed status epilepticus andsurvive. Of these rats,47(78%) displayed spontaneous recurrent seizures invideo and epileptiform discharges on EEG in chronic phase.2. Compared with sham stimulation group and model group, rats in therTMS treated group showed a significant reduction in the number of seizures(P<0.01) during the two weeks of rTMS treatment.3. The expression of MDPR: the PGP, MRP1, MVP were found in theneurons of hippocampal CA3region. Their immunohistochemical positivesignals, which took on brown granules, distributed in the cell membrane andcytoplasm. The nuclei of these neurons had no staining.4.Dynamic expression of MDPR:(1) PGP: it was increased remarkabl-yin the neurons of CA3region in the non-stimulus group compared with that inthe control group, and the difference attained the statistically significant level(P<0.05); it had variable reduction in the rTMS treated group when comparedwith that in the non-stimulus group: its reduction could be found after the firstday’s termination of rTMS administration but with no significa-nce (P>0.05),whereas, this reduction got to significant level both on the7th day and14thday after the termination of rTMS treatment (both P<0.05).(2)MRP1: it was increased significantly in the neurons of CA3regionover the time in the non-stimulus group compared with that in the control group (all P<0.05); it declined gradually in the rTMS treated group whencompared with the non-stimulus group, and its reduction on the first day,7thday and14thday after the termination of rTMS treatment all reached statist-ical significance (all P<0.05).(3) MVP: it was elevated in the neurons of CA3region in the non-stimulus group compared with that in the control group, and the differenten-ce between the two groups was significant(P<0.05); it decreasedgradually with the increase of the time after rTMS treatment when comparedwith the non-stimulus group, and the differences between the two groups onall three time points (the first day,7thday, and14thday) were significant (allP<0.05).Conclusion:1. Low-frequency rTMS shows remarkably an inhibitoryeffect on the epileptic seizures and epileptiforn discharges in the lithiumchloride-pilocarpine induced chronic epilepsy rat model.2. The expression of multidrug resistance protein PGP, MRP1and MVPin the CA3region of lithium-pilocarpine induced chronic epilepsy rat modelall increases significantly, and this might be one of its multidrug resistancemechanisms for this chronic epilepsy rat model.3.Low-frequency rTMS shows an inhibitory effect on the overexpressi-on of PGP,MRP1,MVP in the neurons of CA3region and this inhibitory effectenhances with the increase of the time after14d’s rTMS treatment.4. The inhibitory modulation of low-frequency rTMS on the expressionof three multidrug resistance protein PGP, MRP1and MVP might be one of its important antiepileptic mechanisms. It is hopeful that low-frequency rTMSwould become a novel means to treat refractory epilepsy.