The elucidation of the onset organization of the trigeminal neuralgia using a trigeminal nerve damage animal.

口面部有皮肤和粘膜两个区域，福尔马林注射到这两个不同的区域引起不同的伤害反应行为。将稀释的福尔马林皮下注射到大鼠上唇中比注射到舌头中诱导更多的伤害性行为。预先给予GABA_A受体拮抗剂荷包牡丹碱对福尔马林口唇注射的抑制作用大于舌注射。由此产生的伤害反应行为和药理学的差异可能是由C-纤维群体的数量和质量分布的差异引起的。舌C纤维区三叉神经的初级传入神经元比唇皮少，三叉神经尾侧亚核（Vc）的第Ⅰ层和第Ⅲ层有较多的P物质（SP）、神经激肽-1（NK-1）受体。我们已经消除了这些NK-1轴承神经元预先管理SP共轭核糖体失活毒素，皂草素（SP-Sap）到大鼠枕大池。在这些SP-Sap预处理的大鼠中，福尔马林诱导的疼痛反应行为减少，预先给药荷包牡丹碱增强了疼痛反应行为，而荷包牡丹碱降低了幼稚大鼠的疼痛反应行为。这些结果表明，NK-1阳性神经元通过上行和下行伤害性促进环参与伤害性感受的传导，其中GABA起伤害性感受的作用。

The orofacial region has skin and mucous region and the formalin injection into the two different region induces different nocifensive behavior. The subcutaneous injection of diluted formalin into the rat upper lip induced more nocifensive behaviour than into the tongue. The behavior was inhibited more by the preadministration of an antagonist of GABA_A receptor, bicuculline, when formalin was injected into the lip than into the tongue. The resultant differences of nocifensive behaviour and pharmacology could be caused by the differences in the quantitative and qualitative distribution of C-fiber population. The tongue has fewer primary afferent neurons (trigeminal nerve) in the range of C-fiber than the lip skin.Considerable number of neurons-bearing receptors of substance P (SP), neurokinin-1 (NK-1) are distributed in lamina I and less in lamina III of trigeminal subnucleus caudalis (Vc). We have eliminated these NK-1-bearing neurons by preadministration of SP conjugated with a ribosome-inactivating toxin, saporin (SP-Sap) into the rat cisterna magna. In these SP-Sap-pretreated rats, the formalin-induced nocifensive behaviour was reduced and the preadministration of bicuculline enhanced the nocifensive behaviour, when bicuculline reduced it in the naive rats. These results show that NK-1-bearing neurons are involved in pro-nociceptive transducer through ascending and descending nociceptive facilitating loop, where GABA acts as prpnociceptive.