椎管注射PPADS对内脏痛大鼠行为学及胸髓P2X_7受体表达的影响

Effects of intrathecal PPADS on the behavior and expression of P2X_7 receptor in thoracic spinal cord in visceral pain model rats

目的观察预先椎管注射嘌呤能受体阻滞剂磷酸吡哆醛(PPADS)后,对腹腔注射乙酸致内脏痛大鼠行为学及脊髓P2X7受体和fos免疫组化反应的影响。方法 32只雄性SD大鼠分为空白组、模型组、PPADS组和NS组,每组8只。NS组:先向大鼠鞘内注射20μl NS,注射90 min后再做内脏痛模型。模型组:将0.6%乙酸注射入大鼠腹腔内造成内脏痛模型。PPADS组:先向大鼠椎管鞘内注射10μl PPADS(10 nmol/μl),90 min后按前述方法再做内脏痛模型。实验结束后先记录60min各组动物的腹部收缩试验,然后对各组动物脊髓胸段内P2X7受体和fos进行免疫组织化学染色。结果除空白组,各实验组大鼠均出现明显的腹部收缩试验,其中PPADS组内脏痛指数较模型组明显减轻(P<0.01)。免疫组化染色发现各实验组P2X7和fos阳性表达产物主要表达于胸髓后角浅层内,有明显的定位特点。其中各实验组P2X7阳性表达没有明显变化;而PPADS组的fos阳性数目较模型组明显减少(P<0.01)。模型组与NS组之间P2X7受体和fos表达没有统计学差异。结论脊髓P2X7受体参与腹腔注射乙酸致内脏痛大鼠的痛觉信息传递,其作用与影响其周围的神经元功能活动有关。

Objective To explore the effects of pre-intrathecal injection of pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid（PPADS） on the changes of the behavior and the immunoreactive expression of P2X7 receptor and fos in thoracic spinal cord in visceral pain（VP） model rats.Methods Thirty-two male SD rats were randomized into 4 groups：blank control group,VP model group（VP group）,PPADS group,and NS group.The rats were injected intraperitoneally with 0.6% acetic acid to induce the model in VP group.The rats were intrathecally injected with PPADS in PPADS group and normal saline in NS group 90 min before intraperitoneal injection of acetic acid.The degree of visceral pain was evaluated by the numbers of acetic acid writhing in 60 min.The thoracic spinal cord was stained to detect the expression of P2X7 receptor and fos.Results The obvious writhing activities were found in VP group,PPADS group and NS group.Compared with VP group,the degree of VP index（VPI） was significantly decreased in PPADS group（P0.01）.The immunoreactive positive expression of P2X7 receptor and fos was mainly found in dorsal horn of thoracic spinal cord,predominantly in the superficial layer.No significant difference of positive P2X7 receptor expression was found among VP group,PPADS group and NS group.The image analysis demonstrated that the number of positive fos was significantly lower in PPADS group than in VP group（P0.01）.There was no significant difference in expression of P2X7 receptor and fos between VP group and NS group.Conclusion The P2X7 receptor in spinal cord may play an important role in trasmitting the pain signal function in VP model rats induced by acetic acid.This function may be connected with its influence on activity of the surrounding neurons in thoracic spinal cord.