NMDA receptor subunits NR1, NR2A and NR2B protein expression changes after flurothyl-induced recurrent seizures in the brains of developing rats

SUMMARY Objective: To study NMDA receptors (NR) subunits NR1, NR2A and NR2B protein expression changes after flurothyl induced recurrent seizures in the brains of developing rats. Methods: The rats were induced to have recurrent seizures (30 times) by flurothyl inhalation and decapitated on days 1,3,and 7 after the last seizure respectively. We used immunohistochemical staining to demonstration NR1, NR2A and NR2B in brain sections (12 μm each) mounted on slides. Results: The NR1 protein expressions showed up regulation in dentate gyrus and hippocampus CA1-CA3 at day 1 after the last one of the recurrent 30 seizures,and were 135.2%, 144.7%, and 146.3% compared with control ( P 0.01) respectively. On day 3 after seizures, NR1 protein expressions decreased but were also higher in hippocampus CA1 and CA3, and were 133.8%, 125.7% compared with control ( P 0.05). On day 7 after seizure, NR1 protein expressions in all observed brain areas returned to near normal. The NR2A protein expressions increased in dentate gyrus and hippocampus CA1-CA3 on day 1 after seizures,and were 135.6%, 129.4%, and 130.5% compared with control ( P 0.01) respectively.On day 3 after seizures, NR2A protein expression was also higher than that before seizure, butthe difference was not significant. On day 7 after seizure, NR2A protein expression returned to normal. NR2B moderately increased in dentate gyrus and hippocampus CA1-CA3 on day 1 and 3 after seizures, but the difference was not significant. Conclusion: The NR1 protein expression up regulated in dentate gyrus and hippocampus CA1-CA3 after 30 recurrent seizures, and lasted for 3 days after the last seizure in hippocampus CA1-CA3. NR2A protein expression up regulation only occurred at day 1 after seizures in all areas observed, whereas the NR2B showed no significant increase. These suggest that the NR subunits composition in the immature brain may change after recurrent seizures,which may have a long term effect on the excitability and development of the brain.