雌激素对福尔马林致痛后小鼠脊髓背角c-Fos和P物质的影响

Effect of estrogen on expressions of c-Fos and substance P in dorsal horn of spinal cord in mice following formalin stimulation

目的观察雌激素对福尔马林致痛后小鼠痛觉评分及脊髓背角c-Fos和P物质(SP)表达的影响。方法选用雌性C57/BL6小鼠15只,分成对照组(control)、去卵巢手术组(OVX+V)、去卵巢手术加雌激素组(OVX+E),每组5只。采用痛觉评分分析雌激素对小鼠福尔马林足底注射后痛行为的影响,结合c-Fos及SP免疫组化,观察雌激素对脊髓L3～L5节段背角浅层神经元激活及痛觉传入的影响。结果小鼠福尔马林致痛后control组、OVX+V组和OVX+E组在第一时相的痛觉评分组间无统计学差异(P>0.05);间歇期及第二时相早期的痛觉评分OVX+V组明显高于control组和OVX+E组(P<0.05)。卵巢摘除增加福尔马林致痛后引起的脊髓背角FLIN数(P<0.01)和SP免疫阳性反应物,而雌激素能有效抑制福尔马林引起的注射侧背角FLIN数的升高(P<0.01)以及SP免疫阳性反应物显著降低。结论雌激素通过调节脊髓背角浅层感觉神经元的活动及痛觉纤维的传入参与对小鼠福尔马林致痛的镇痛作用。

Objective To investigate the effect of estrogen on the pain score, c-Fos and substance P expressions in the dorsal horn of the spinal cord in the mice following formalin stimulation. Methods Fifteen C57/BL6 mice were randomized to 3 groups ： control group （ intact mice without estrogen treatment）, OVX ＋ V group （ ovariectomized mice given vehicle＇ and OVX ＋ E group （ ovariectomized mice with subcutaneous injection of 2 μg/d 17β-estradiol for 10 d）. Pain score was used to assay the role of estrogen in affecting pain threshold in the mice following formalin injected into the right hind paw, and expressions of c-Fos and substance P in the dorsal horn of spinal cord （ L3 to L5 ） in 2 h after injection of formalin was tested with immunohistochemisty to evaluate neuron activity and pain afferent fibers. Results Pain score was increased in ovariectomized mice following formalin stimulation, which was inhibited by estrogen especially in the early stage of secondary phase. The number of c-Fos-like immunoreactivity neuron （FLIN, P 〈0.01 ） and substance P immunoreactivity in the dorsal horn of spinal cord was increased in ovariectomized mice, which was reversed by estrogen. Conclusion Estrogen exerts analgesic effect in OVX mice, which maybe mediate through modulating sensory neurons and afferent fibers in the superficial dorsal horn of the spinal cord.