Changes of NMDA receptor binding nature in rat brain and spinal cord following noxious stimulation

NMDA受体似乎参与了伤害性神经元的激活。由福尔马林或炎症介质产生的背角伤害性神经元的超兴奋性可被NMDA拮抗剂阻断。但目前尚不清楚伤害性激活如何改变NMDA受体的结合性质。本研究探讨了大鼠在伤害性感受过程中NMDA受体水平的变化。(1)将弗氏完全佐剂注射到大鼠的后爪种植区。表现为对注射足的压力和肿胀的痛敏反应，持续10-14天。(2)测定伤害性处理大鼠和对照组大鼠脊髓和脑脊膜上NMDA拮抗剂~3H-MK801的结合。饱和结合数据的Scatchard图显示，炎症大鼠脊髓的Bmax(最大特异性结合)增加，Kd值(平衡解离常数)无变化。但我们没有看到从整个大脑、皮质和海马区结合的Bmax或Kd有任何变化。这些结果表明，在弗氏完全佐剂注射的动物中，脊髓NMDA受体表达上调。

NMDA receptors appear to be involved in activation of nociceptive neurons. The hyperexcitability of dorsal horm nociceptive neurons produced by formalin or inflammatory agents is blocked by NMDA antagonists. But it is not clear how nociceptive activation may alter NMDA receptor binding nature. This study investigated changes in NMDA receptor level during nociception.(1) Rats received a subcutaneous injection of Freund's complete adjuvant into planter aspect of a hindpaw. They displayd hyperalgesia to pressure and edema of the injected paw for 10-14 days. A week after this treatment, rats were decapitated and brain and spinal cord were removed rapidly.(2) The binding of ^3H-MK801 (NMDA antagonist) to brain and spinal cord membranes prepared from nociceptive treatment and control rats was determioned Scatchard plot of the saturation binding data revealed an increase in Bmax (maximum specific binding) and no change in the Kd values (equilibrium dissociation constants) of this ligandbindings obtained fron spinal cord of inflammed rats as compared to controls. But we failed to see any change in the Bmax or Kd for binding from whole brain, cortex and hippocampus. These results indicate that spinal NMDA receptor are up-regulated in Freund's complete adjuvant injected animalsl.