电针对慢性内脏痛敏大鼠脊髓背角c-fos蛋白表达的影响

目的：针刺治疗对肠易激综合征（irritable bowel syndrome，IBS）患者的慢性腹痛具有良好疗效，然而，其神经生物学机制仍不清楚。本研究在电针缓解IBS模型大鼠慢性内脏痛敏基础上，观察和分析IBS大鼠脊髓背角中内脏反应神经元的兴奋性在针刺治疗前后的改变，探讨针刺缓解IBS模型大鼠慢性内脏痛敏的机制。方法：采用新生9d的Sprague-Dawley雄性幼鼠，通过结直肠机械扩张刺激制作IBS慢性内脏痛敏模型。饲养至648周后，观察大鼠由结直肠扩张诱发的腹部撤回反射（abdominalwithdrawreflex，AWR）评分变化。电针组穴位取双侧＂足三里＂和＂上巨虚＂，连续隔日治疗4次，假电针组不通电，其余与电针组同。治疗结束后，取材并用免疫组化方法观察各组大鼠脊髓背角中c-los蛋白表达的变化。结果：与正常大鼠比较，IBS模型大鼠AwR评分明显升高（P〈0．01），电针治疗后AwR评分明显降低（P〈0．05）；与正常大鼠相比，IBS模型大鼠脊髓L6-S2节段浅层（superficiallaminae，SDH，laminaeⅠandⅡ）、固有层（nucleusproprius，NP，laminaeⅢandⅣ）、背角颈段（neckofdorsalhorn，NECK，laminaeVandVI），以及T13-L2节段的NECK中，c-los阳性神经元明显高于正常对照组（P〈0．05），而电针治疗后IBS大鼠脊髓L6-S2节段SDH、NP、NECK以及T13-L2节段的NECK亚区中，c-los阳性神经元明显下降（P〈0．05）；假电针对AWR评分、c-los蛋白表达没有影响。结论：电针可以明显抑制IBS模型大鼠脊髓背角中内脏反应神经元异常增高的兴奋性，这可能是针刺缓解慢性内脏痛敏的机制之-。

Effects of electroacupuncture on expression of c-fos protein in the spinal dorsal horn of rats with chronic visceral hyperalgesia

OBJECTIVE： Acupuncture is widely used in clinics to suppress chronic visceral pain in patients with irritable bowel syndrome （IBS）; however, the exact neurobiological mechanisms for its therapeutic effects need further exploration. The aim of this study was to investigate the possible involvement of spinal neurons in the effects of electroacupuncture （EA） in relieving chronic visceral hyperalgesia in a rat model of IBS. METHODS： Colon mechanical irritation was applied to male neonatal Sprague-Dawley rats to establish the IBS model. Behavioral test of the abdominal withdraw reflex （AWR） response to colorectal distention stimuli was conducted to judge the degree of colorectal sensitivity. EA at acupoints Zusanli （ST36） and Shangjuxu （ST37） was applied bilaterally in a total of four times every other day, while sham-EA at similar acupoints was done by inserting needles without electrical stimulation, Immunohistochemical methods were used to display the expression of proto-oncogene protein c-fos in the spinal dorsal horn. RESULTS： It was found that AWR scores were significantly increased in the IBS model rats （P〈 0.01）, accompanied with significant increase in the expression of c-fos protein in the superficial laminae （SDH, laminae Ⅰ and Ⅱ ） and nucleus proprius （NP, laminae Ⅲ and Ⅳ）, the neck of the dorsal horn （NECK, laminae V and Vl） at lumbosacral （L6-S2） spinal level, and in NECK at thoracolumbar （T13-L2） spinal level, when compared with normal rats （P〈0. 05）. After EA treatment, AWR scores and the expression of c-fos protein in SDH, NP and NECK at similar spinal levels were significantly decreased in the IBS model rats （P〈0.05）. No such effects on either AWR scores or the expression of c-fos protein were observed in IBS model rats after sham-EA treatment. CONCLUSION： The abnormally high neuronal excitability in the spinal dorsal horn may be an important reason underlying the visceral hyperalgesia in IBS model rats. EA treatment can relieve the chronic visceral hyperalgesia in IBS rats by suppressing the abnormal neuronal excitability in the spinal dorsal horn.