正中神經以磷脂醯膽鹼處理活化甘丙肽類型2受器 在機械性觸覺痛扮演的角色

Abstract

先前的研究發現，磷脂醯膽鹼會造成神經髓鞘剝離退化，並引發感覺疼痛異常，如：觸覺性疼痛和痛覺過敏等現象。本研究藉由磷脂醯膽鹼藥物處理，誘發正中神經局部去髓鞘化，再利用免疫細胞化學分析、動物疼痛行為測試，進一步探討甘丙肽類型2受器在神經病變疼痛中所擔任的機制。首先證實正常大白鼠的第六頸髓段背根神經節表現甘丙肽類型2受器免疫反應神經元為小型神經元，於正中神經4%磷脂醯膽鹼處理一週，背根神經節中甘丙肽類型2受器免疫反應神經元百分比有明顯地增加。進一步以雙重螢光免疫標誌法分析第六頸髓段背根神經節內甘丙肽類型2受器免疫反應神經元是否有神經絲蛋白200, 轉錄活化因子3, 生長相關因子43, 甘丙肽, 神經胜肽Y, 物質P, 神經性一氧化氮合成酶, 辣椒素受器1。結果顯示同時與神經絲蛋白200, 轉錄活化因子3及神經胜肽Y共存的百分比有顯著地增加；但與物質P共同表現的百分比卻是降低。結果顯示磷脂醯膽鹼處理後，誘導甘丙肽類型2受器免疫反應神經元增升部分為大型受傷的神經元且同時具有神經胜肽Y的表現。另外，動物行為測試分析正中神經施以4%磷脂醯膽鹼處理，在動物同側前肢呈現觸覺痛及溫熱覺過敏現象；當其同側前肢掌面皮下注射甘丙肽類型2受器拮抗劑M871或增效劑AR-M1896處理時，分析其行為反應及楔狀神經核內原致癌基因免疫反應神經元的數量變化。結果發現觸覺痛及楔狀神經核內原致癌基因免疫反應神經元數量以M871處理有顯著地緩解並數量下降，而施以AR-M1896有加劇且數量增加。綜合以上結果，推測磷脂醯膽鹼處理誘導甘丙肽類型2受器免疫反應神經元的增升可能透過神經胜肽Y的釋放，而促使楔狀神經核內原致癌基因免疫反應神經元的數量增加，而與觸覺痛訊息的傳遞有所關聯。

Previous studies have revealed that lysophosphatidylcholine could induce nerve demyelination and initiate neuropathic pain, such as allodynia and hyperalgesia. This study used lysophosphatidylcholine inducing the median nerve local demyelination, and then we investigated the role of galanin receptor 2 (GalR2) in neuropathic pain by immunohistochemistry, drug treatment and animal behavioral test. First, we found galanin receptor 2- like immunoreactive (GalR2-IL) production localized in the small-sized C6 dorsal root ganglion neurons of the normal rats, but the amount of GalR2-IL neurons peaked at one week after lysophosphatidylcholine treatment. Furthermore, we used double immunofluorescence of GalR2-IL neurons weather contained NF200, ATF-3, GAP43, Galanin, NPY, SP, nNOS, VR1. The results showed that the percentage of GalR2-IL neurons also labeled NF200, ATF3, NPY were increasing, but decreased in for SP. These results suggested that lysophosphatidylcholine treatment up-regulated GalR2 expression in A-type and injury DRG neurons further containing NPY. After 4% lysophosphatidylcholine treatment in the median nerve, animals developed tactile allodynia and thermal hyperalgesia in treated side of forelimb. Moreover, we employed lysophosphatidylcholine treatment along with GalR2 agonist (AR-M1896) or antagonist (M871) intraplantar application to examine the effect on median neuropathic pain and c-Fos expression in the stimulated side in cuneate nucleus (CN). The mechanical allodynia level and the number of c-Fos-IL neurons in the M871 group were dramatically attenuated, whereas those in the AR-M1896 group had increased compared to the saline group. These results indicated that activation lysophosphatidylcholine -upregulated GalR2-IL neurons may be possibly via promoting NPY release to evoke c-Fos expression in the CN and to transmit LPC-induced tactile hypersensitivity.