Florenzano F, De Luca B
Institute of Anatomy and Histology, University of Verona, Italy.
Neuroscience. 1999 Apr;90(1):201-7. doi: 10.1016/s0306-4522(98)00388-1.
The dorsal horn of the subnucleus caudalis of the spinal trigeminal nucleus is a relay of oro-facial pain transmission; increase in subnucleus caudalis neuronal activity in response to tissue injury affects the level of chemical mediators participating in nociceptive processing. We investigated, by means of immunocytochemistry, the expression of N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) glutamate receptor subunits in this nucleus in a model of inflammation. Rats injected with formalin in the whisker pad were compared with saline-injected control rats. One and two days after formalin injection, the immunostaining of cell bodies and neuropil of the AMPA receptor subunits GluR1 and GluR2/3 was markedly decreased in the ipsilateral superficial laminae of the subnucleus caudalis compared to the contralateral side. Side differences were not evident in the saline-treated animals. The down-regulation of AMPA GluR1 and GluR2/3 was no longer detectable in the subnucleus caudalis three days after formalin injection. No side difference was detected in the N-methyl-D-aspartate receptor subunit NR2A/B immunoreactivity of the subnucleus caudalis at any time-point in the formalin-injected animals. The modulation of AMPA receptor may be related to the decrease of hyperalgesia evident 1 h after formalin injection, in spite of the increasing perioral inflammation evident later on and characteristic of the formalin model. The present findings point out a selective down-regulation of AMPA receptor subunits in the transduction of trigeminal pain. These data also support the involvement of glutamate receptor subunits in the processing of trigeminal inflammation induced by noxious chemical stimulation.
三叉神经脊束核尾侧亚核的背角是口面部痛觉传递的中继站；对组织损伤做出反应时，尾侧亚核神经元活动的增加会影响参与伤害性处理的化学介质水平。我们通过免疫细胞化学方法，研究了炎症模型中该核团内N-甲基-D-天冬氨酸和α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）谷氨酸受体亚基的表达。将在须垫注射福尔马林的大鼠与注射生理盐水的对照大鼠进行比较。与对侧相比，福尔马林注射后1天和2天，尾侧亚核同侧浅层层内AMPA受体亚基GluR1和GluR2/3的胞体和神经纤维网免疫染色明显减少。在生理盐水处理的动物中未观察到侧别差异。福尔马林注射后3天，尾侧亚核内AMPA GluR1和GluR2/3的下调不再可检测到。在福尔马林注射动物的任何时间点，尾侧亚核的N-甲基-D-天冬氨酸受体亚基NR2A/B免疫反应性均未检测到侧别差异。尽管福尔马林注射后1小时痛觉过敏明显减轻，但随后口周炎症逐渐加重，这是福尔马林模型的特征，AMPA受体的调节可能与痛觉过敏的减轻有关。目前的研究结果指出了AMPA受体亚基在三叉神经痛传导中的选择性下调。这些数据也支持谷氨酸受体亚基参与了有害化学刺激诱导的三叉神经炎症的处理过程。
