地佐环平对边缘叶癫痫发作大鼠海马P-糖蛋白表达的影响

目的 观察兴奋性谷氨酸受体（NMDA受体）拮抗剂地佐环平（MK801）对边缘叶癫痫大鼠发作后P-糖蛋白（P—gp）表达的影响,探讨NMDA受体是否能对癫痫发作后P—gp表达进行调控。方法 制备氯化锂．匹罗卡品癫痫发作大鼠模型,60只大鼠,随机分为6组：对照组、癫痫发作终止后0、3、6、24和72h组,用实时荧光定量RT-PCR检测癫痫大鼠发作终止后不同时程海马组织P—gp mRNA的表达。另取60只大鼠随机分为对照组、癫痫持续状态发作模型（SE）组、MK801干预组,各组均分为发作终止后6h和24h时间点。用实时荧光定量RT—PCR检测癫痫发作终止后6h大鼠海马P-gp mRNA的表达,用免疫组化检测大鼠癫痫发作终止后24h海马组织P—gp蛋白的表达。结果 癫痫发作终止后72h内的所有动物海马组织多药耐药基因1a（mdr1a）的表达均显著高于对照组,SE终止即刻其表达显著升高5．6（2．9）×10^5 mRNA拷贝数／40ng总RNA,P〈0．05],SE终止后3h时其表达进一步升高7．6（6．3）×10^5,P〈0．01],此后至SE终止后72h,mdrla mRNA的表达一直维持在该水平;mdr1b的表达在边缘叶发作动物呈一过性增高,发作终止后3、6h分别为（3．3±0．4）×10^4和（3．6±1．0）×10^4,为对照组的2．2、2．4倍]均明显高于对照组（P〈0．01）。另外,在发作终止后6h时,MK801组mdr1a（4．3±0．8）×10^5]和mdr1b（2．0±0．7）×10^4]基因表达明显低于SE组（P〈0．01）;发作终止24h时,MK801组P—gp（26．6±5．0）个微血管／400倍视野]蛋白表达也明显低于SE组（39．0±4．1）个微血管／400倍视野,P〈0．01]。结论 NMDA受体拮抗剂MK801下调癫痫大鼠发作后P-gp的过度表达,提示NMDA受体可能参与癫痫发作过程中P—gp表达的调控,有效抑制NMDA受体的过度活化可能有助于防止癫痫发作后P—gp的过度表达。

Effect of dizocilpine on P-glycoprotein expression in hippocampus in limbic seizure: experiment with rats

OBJECTIVE: To observe the effect of dizocilpine (MK801), a noncompetitive antagonist of N-methyl-D-aspartic acid (NMDA) receptor, on P-glycoprotein (P-gp) expression after limbic seizure, and to explore whether NMDA receptor play a role in the regulation of P-gp expression during limbic seizure. METHODS: 120 Wistar rats were randomly divided into 2 equal sets. 50 rats in Set 1 underwent intraperitoneal injection of lithium chloride, scopolamine, and pilocarpine so as to cause status epilepticus (SE) for 90 min. Then diazepam was given to terminate the SE. The rats were killed 0, 3, 6, 14, and 72 h after the SE respectively. The hippocampus was isolated. Realtime fluorescent quantitative RT-PCR (qRT-PCR) was used to detect the expression of multidrug resistance gene 1a (mdr1a) and mdr1b. Immunohistochemistry was used to detect the P-gp. The rats were used as controls. Another 60 rats (Set 2) were randomly divided into 3 equal groups: control group, given with normal saline (NS) only, SE group, given with NS 20 min before administration of pilocarpine, and MK801 group, given with MK801 20 min before administration of pilocarpine. The 3 groups in Set 2 were further divided into 2 equal subgroups of 10 rats to be killed 6 or 24 h after SE. RESULTS: The mdr1a expression in hippocampus within 72 h after seizure was much higher at each time point: the level of mdr1a expression instantly after the seizure was terminated was 5.6 (2.9) x 10(5) mRNA copies/40 ng total RNA], significantly higher than that of the controls 2.4 (1.1) x 10(5) mRNA copies/40 ng total RNA, P < 0.05], increased to the level of 7.6 (6.3) x 10(5), P < 0.01] 3 h after, and kept at such level till 72 h after. The msr1b expression transiently increased 2.2 and 2.4 times that of the controls respectively 3 h and 6 h after the seizure was terminated (3.3 +/- 0.4) x 10(4), and (3.6 +/- 1.0) x 10(4), both P < 0.01)]. The expression level of mdr1a 6 h after the seizure was terminated of the MK801 group was (4.3 +/- 0.8) x 10(5) and the expression level of mdr1b 6 h after the seizure was terminated of the MK801 group was (2.0 +/- 0.7) x 10(4), both significantly lower than those of the SE group (both P < 0.01). The P-gp expression level 24 h after the seizure was terminated of the MK801 group was 26.6 +/- 5.0 pieces of microvessels/400 times field, significantly lower than that of the SE group (39.0 +/- 4.1, P < 0.01). CONCLUSION: MK801 down-regulates the overexpression of P-gp after seizure, which indicates that NMDA receptor may be involved in the regulation of P-gp expression during seizure. Therefore, it is possible to prevent the overexpression of P-gp after seizure by inhibiting NMDA receptor's overactivation effectively.