电针对慢性内脏痛觉敏感大鼠延髓头端腹内侧核c—fos蛋白和NRl受体表达的影响

目的：针刺治疗对肠易激综合征（irritablebowelsyndrome,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（electroacupuncture,EA）缓解IBS模型大鼠慢性内脏痛觉敏感的基础上,观察和分析IBS大鼠延髓头端腹内侧核（rostralventromediamedulla,RVM）中内脏反应神经元的兴奋性在针刺治疗前后的改变,以及RVM中N-甲基-D-门冬氨酸1型受体（N-methyl～D-aspartatereceDtor1,NRl）在针刺缓解IBS模型大鼠慢性内脏痛敏中的参与机制。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慢性内脏痛觉敏感模型,持续两周。饲养6～8周后,观察大鼠由结直肠扩张（colorectaldistention,CRD）诱发的痛阈压力值（painthresholdpressure,PTP）和腹部撤回反射（abdominalwithdrawalreflex,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,其余与电针组相同。治疗结束后,取材并用免疫组织化学方法观察各组大鼠RVM中c—fos蛋白和NRl受体的表达变化。结果：与正常大鼠相比,成年IBS模型大鼠PTP值明显降低,且AWR评分明显升高（P〈0．01）;与电针治疗前相比,IBS大鼠电针治疗后PTP值明显升高（P〈0．01）,AWR评分明显降低（P〈0．05）;与正常大鼠相比,IBS模型大鼠RVM各个亚核包括中缝大核（nucleusraphemagnus,NRM）、网状巨细胞核a部（nucleusreticularisgigantocellularisparsalpha,GiA）、外侧旁巨细胞核（nucleuslateralisparagigantocellulari,LPGi）以及网状巨细胞旁核（nucleusreticularisgigantocellularis,Oi）中c—fos蛋白和NRl受体阳性神经元的计数明显升高（P〈0．05）,而电针治疗后Gi、LPGi、GiA中c—fos蛋白,以及Gi、LPGi、GiA、NRM中NRl受体免疫阳性神经元的计数与接受电针治疗前相比明显下降（P〈O．05）;假电针对PTP、AWR、c～los蛋白和NRl受体阳性神经元的计数没有影响。结论：电针可以明显抑制IBS模型大鼠RVM中内脏反应神经元兴奋性异常增高,同时电针能明显抑制IBS模型大鼠RVM中NRl受体表达,这可能是RVM中内脏反应神经元异常增高的兴奋性下降的重要原因,同时也是针刺缓解慢性内脏痛觉敏感的机制之一。

Effects of electroacupuncture on expression of c-fos protein and N-methyl-D-aspartate receptor 1 in the rostral ventromedia medulla of rats with chronic visceral hyperalgesia

OBJECTIVE： Acupuncture has been clinically proved to be effective in treating abdominal pain in patients with irritable bowel syndrome （IBS）. However, its neurobiological mechanism remains largely unexplored. The aim of this study was to investigate the effect of electroacupuncture （EA） in relieving chronic visceral hyperalgesia and the possible involvement of N-methyi-D- aspartate receptor I （NR1） in rostral ventromedia medulla （RVM） of the brain in an IBS rat model. METHODS. To establish the IBS rat model, male Sprague-Dawley neonatal rats received colon mechanical irritation on a daily basis from the 9th to the 22rid day after their birth. After a resting period of another two to four weeks, behavioral tests of pain threshold pressure （PTP） and abdominal withdrawal reflex （AWR） responding to colorectal distention （CRD） stimuli were conducted to judge the colorectal sensitive situation. Then administration of EA at acupoints of Zusanli （ST36） and Shangjuxu （ST37） bilaterally in the hind limbs was repeated four times every other day, while sham-EA was done by inserting needles at similar acupoints without electrical stimulation. Immunohistochemical method was used to display the expression of proto- oncogene protein c-los and NR1 in RVM of rats. RESULTS.- The results demonstrated that the PTP values and AWR scores, in response to the CRD stimuli, significantly decreased and increased, respectively （P〈0.01, P〈0.01）, while the number of immunoreactive neurons of c-los protein and NR1 significantly increased in nucleus reticularis gigantocellularis （Gi）, nucleus lateralis paragigantocellulari （LPGi）, nucleus reticularis gigantocellularis pars alpha （GiA） and nucleus raphe magnus （NRM） of RVM in IBS model rats compared with the normal rats （P〈0.05）. After EA treatment, PTP values and AWR scores significantly increased and decreased, respectively （P〈0.01, P〈0.05）; the number of immunoreactive neurons of c-los and NR1 significantly decreased respectively in Gi, LPGi and GiA and in Gi, LPGi, GiA and NRM （P〈0.05）. No such effects on PTP values, AWR scores and the number of immunoreactive neurons of c-fos and NR1 were observed after sham-EA treatment. CONCLUSION： These data provide the evidence that EA can relieve chronic visceral hyperalgesia in rats with IBS, and such an effect may be correlated with inhibitory modulation of hyperactivity of neurons by means of down-regulating the high expression of NR1 in RVM of IBS model rats,