新生大鼠反复惊厥对NMDA受体表达的长期影响

目的：研究反复惊厥对大鼠脑内N-甲基-D-天门冬氨酸(NMDA)受体表达，以及成年期认知功能和惊厥阈的长期影响。方法：生后6d(用P6表示，下同)的Wistar大鼠随机分成两组，每组6只，惊厥组每日吸入三氟乙醚诱导惊厥发作1次，每次持续30min，连续6d；对照组同样操作但不吸入三氟乙醚。两组大鼠于P60-P65行Morris水迷宫实验，检测大鼠的学习记忆功能。于P75时给予大鼠腹腔注射戊四唑(PTZ)测定大鼠的惊厥阈。随即断头处死大鼠，分离大脑皮质和海马，匀浆提取细胞膜蛋白，应用免疫印记法测定NMDA受体亚基l(NRl)和NR2A-2D表达的变化。结果：从P6l至P65，两组大鼠寻找平台时间均逐渐缩短，惊厥组大鼠在P65的平均寻找平台时间较对照组显著延长。惊厥组大鼠注射PTZ后发生惊厥的潜伏期与对照组比较差异无显著性。在大脑皮层，惊厥组大鼠较对照组NRl和NR2B表达水平明显下调，在海马这两种亚基表达水平无明显改变，在大脑皮层和海马区，惊厥组较对照组NR2A表达水平明显下调，NR2C表达水平明显上调。两组在皮层和海马均无NR2D表达。结论；新生大鼠反复惊厥可导致远期认知障碍，同时伴有NMDA受体的数量和结构上的长期改变，NMDA受体表达的这种改变可能在发育期惊厥导致的脑长期认知功能损害中起重要作用。

Long-term effects of recurrent seizures in neonatal rats on NMDA receptor expression in the brain

Objective:To study the long term effect of flurothyl induced recurrent seizures in neonatal rats on cognition, seizure susceptibility, and NMDA receptor expression in adult rat brain. Methods:Seizures were induced by inhalant flurothyl for 6 days, starting from postnatal day 6 (P6). On P60, rats were tested for spatial memory by using the Morris water maze task. Seizure threshold was examined by intraperitoneal injection of pentylenetetrazol (PTZ) on P75. Brain homogenates were made at the same time. Expression of NMDA receptor protein in cerebral cortex and hippocampus was examined with Western blotting analysis. Results: Compared with the control group, flurothyl treated rats showed significant spatial deficits in the Morris water maze on P60. There was no difference in seizure threshold. In the cerebral cortex of flurothyl treated rats, the protein expressions of NR1, NR2A, and NR2B decreased significantly, but NR2C increased significantly. In the hippocampus of flurothyl treated rats, the protein expression of NR2A decreased significantly, the protein expression of NR2C increased significantly, and NR1 and NR2B were similar to that in the hippocampus of control group. Conclusion: Recurrent seizures in neonatal rats might cause long term cognitive deficit and modify NMDA receptor subunit expressions in cerebral cortex and hippocampus of adult rats. This phenomenon raised the possibility that abnormal NMDA receptor expression might play an important role in long term cognitive deficit induced by early life recurrent seizures.