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

NMDA受体似乎参与了痛觉神经元的激活。由福尔马林或炎症剂产生的背激素痛觉神经元的高兴奋性被NMDA拮抗剂阻断。但目前尚不清楚痛觉激活如何改变NMDA受体的结合性质。本研究探讨了NMDA受体在痛觉过程中的变化。(1)大鼠后爪种植面皮下注射弗氏完全佐剂。它们表现出对注射足部压迫和水肿的痛觉过敏，持续10-14天。治疗一周后，将大鼠斩首，迅速切除脑和脊髓。(2)测定了NMDA拮抗剂^3H-MK801 （NMDA拮抗剂）与损伤性治疗大鼠和对照大鼠制备的脑和脊髓膜的结合，饱和结合数据的Scatchard图显示，与对照相比，炎症大鼠脊髓的这种配体结合的Bmax（最大特异性结合）增加，Kd值（平衡解离常数）没有变化。但我们没有看到全脑、皮质和海马的Bmax或Kd结合有任何变化。这些结果表明，在注射弗氏完全佐剂的动物中，脊髓NMDA受体上调。

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.