大麻二酚改善福尔马林诱导的口腔颌面部炎性痛作用及中枢机制

Analgesia effect and central mechanism of cannabidiol in formalin-induced orofacial inflammatory pain

目的研究大麻二酚(CBD)对口腔颌面部炎性痛的镇痛作用及其中枢机制。方法采用上唇右侧sc给1%福尔马林溶液(37%~40%甲醛)诱发口腔颌面部炎性痛模型。①成年雄性C57BL/6J小鼠随机分为正常对照组、模型组和模型+CBD(0.01,0.03和0.06 mg)组(上唇右侧sc给药),给药5 min后,上唇右侧sc给予1%福尔马林溶液。②成年雄性C57BL/6J小鼠随机分为正常对照组、模型组和模型+CBD 0.06 mg组,给药方式及部位同分组①。观察记录分组①小鼠一相痛(0~6 min)和二相痛(15~45 min)小鼠抓脸时间;行为实验结束45 min后(相当于注射福尔马林90 min后),分组①中每组随机选取4只,采用免疫荧光方法检测小鼠三叉神经脊束核尾侧亚核(Sp5C)和前扣带回(ACC)脑区c-Fos蛋白表达。采用内源性大麻素探针结合光纤记录方法检测分组②中小鼠二相痛时期小鼠中央导水管周围灰质(PAG)、基底外侧杏仁核(BLA)和ACC脑区内源性大麻素水平。结果①与正常对照组相比,模型组小鼠一相痛和二相痛抓脸时间显著延长(P<0.01);与模型组相比,模型+CBD 0.06 mg组二相痛时期小鼠的抓脸时间显著缩短(P<0.01),一相痛时期的抓脸时间无明显变化。免疫荧光结果显示,与正常对照组相比,模型组小鼠Sp5C和ACC的c-Fos阳性神经元数量显著升高(P<0.01);与模型组相比,模型+CBD 0.06 mg组上述2个脑区的c-Fos蛋白表达水平显著降低(P<0.01)。②探针结合光纤记录结果显示,与模型组相比,模型+CBD0.06mg BLA的内源性大麻素水平显著升高(P<0.05);但与正常对照组相比,模型组无显著变化。结论在口腔颌面部炎性痛中,sc给予CBD可通过降低口面部疼痛上行传导通路中Sp5C和ACC脑区c-Fos蛋白表达,上调疼痛下行抑制通路内源性大麻素系统功能,从而发挥镇痛作用。

OBJECTIVE To study the analgesia effect and neurobiological mechanism of local adminis-tration of cannabidiol(CBD)in formalin-induced orofacial inflammatory pain.METHODS The orofacial inflammatory pain model of mice was established by injection of 1%formalin into the right upper lip subcu-taneously.①Male C57BL/6J mice were randomly divided into the control group,model group and model+CBD(0.01,0.03 and 0.06 mg)group.②Male C57BL/6J mice were randomly divided into the normal control group,model group and model+CBD 0.06 mg group.Mice from①were used to evaluate the analgesic effect of CBD(0.01,0.03 and 0.06 mg)which was subcutaneously injected into the right upper lip.Following the conclusion of the behavioral experiment(equivalent to 90 minutes after formalin injec-tion),4 animals were randomly selected from the normal control group,model group and model+CBD 0.06 mg group for immunofluorescence analysis.The immunofluorescence method was employed to assess the expression of c-Fos protein in both the spinal trigeminal caudal subnucleus(Sp5C)and anterior cingulate gyrus(ACC).The endocannabinoid probe was used in combination with optical fiber recording to detect the changes of endocannabinoid levels in central periaquaductal gray matter(PAG),basolat-eral amygdala(BLA)and ACC of mice from②during the second phase of pain.RESULTS In the forma-lin-induced orofacial inflammatory pain model,the total time of rubbing in model group was significantly longer than that of the control group,and subcutaneous administration of CBD(0.03,0.06 mg)signifi-cantly decreased the total time of rubbing(P<0.01).CBD 0.06 mg significantly decreased the face-rubbing time of mice in the second pain period(P<0.01),but had no effect on the first pain period(P>0.05).The number of c-Fos positive neurons in PAG,BLA and ACC in the model group was significantly increased compared with the control group,and local administration of CBD could significantly reduce the expres-sion level of c-Fos in the above three brain areas(P<0.01).In the second phase of pain,subcutaneous administration of CBD increased the level of endocannabinoid in BLA.CONCLUSION In formalin-induced orofacial inflammatory pain,local administration of CBD can reduce the c-Fos expression of Sp5C and ACC,and up-regulate the function of the endocannabinoid system so as to achieve the anti-inflammatory and analgesic effects.