母婴分离致肠易激综合征大鼠模型的建立与评价

Establishment of irritable bowel syndrome rat models with neonatal maternal separation method

目的 研究新生期母婴分离导致肠易激综合征（IBS）大鼠模型的建立及其对P物质与其受体NK1表达的影响。方法将64只新生期雄性大鼠随机分为母婴分离组（在出生后第2～21天，每天将新生大鼠与哺乳期母鼠分离3h）和对照组（不给予上述处理）。成年后（出生后60d）两组大鼠均给予结直肠球囊扩张（CRD），用行为学观察和腹部回缩反射（AWR）评分来评估内脏痛反应，用免疫组化方法检测腰骶段脊髓背角P物质及其受体NK1的表达量，并进行远端结肠常规组织学检测。结果引起母婴分离组大鼠内脏痛反应的CRD压力阈值[（19．22±926）mmHg]显著低于对照组[（24．89±1091）mmHg]，差异有统计学意义（P〈0．05）。在40、60和80mmHg压力扩张下，母婴分离组的AWR评分均显著高于对照组（均P〈0．05）。CRD后母婴分离组腰骶段脊髓背角P物质及其受体NK1蛋白免疫反应阳性细胞数与对照组比较差异均无统计学意义（均P〉0.05）。母婴分离组和对照组大鼠在CRD前后结肠均未见组织损伤或炎症。结论新生期母婴分离能成功建立IBS大鼠模型，成年后在内脏刺激时产生过强的内脏痛反应和神经元活化反应，P物质及其受体NK1可能不参与其过程。

Objective To establish a rat model of irritable bowel syndrome with neonatal maternal separation method. Methods Male neonatal SD rats were randomly divided into 2 groups： in maternal separation（MS） group, the rats were exposed to a 3-h daily maternal separation from d2 to d21, and rats in control group were not exposed to maternal separation. The eolorectal balloon distension （CRD） was performed 60d after birth for assessment of abdominal withdrawal reflex（AWR）, a surrogate marker of visceral pain. Lumbar-sacral spinal cords were harvested for semi-quantitative analysis of substance （SP） and its receptor NK1 in the dorsal horn using immunohistochemical methods. The distal colons were examined with histological analysis before and after CRD. Results Pain threshold was significantly lower in MS than that in control group （19.22± 9.26mmHg vs. 24.89±10.91mmHg, P〈0.05）. The AWR score in response to CRD in MS group was significantly higher than control group at high distension pressures （40 mmHg： 3.49±1.40 vs. 2.80 ±1.34; 60 mmHg： 3.78 ±1.11 vs. 3.16±1.21 ;80 mmHg： 4.26±1.35 vs. 3.61±1.01 ; P〈0.05）. There was no significant difference in the number of SP and NK1 receptor-positive neuron at dorsal horn of lumbar-sacral spinal between MS and control group （38.07 ±9.21 vs. 39.85 ±8.29; 2.26 ±0.54 vs. 2.63 ± 0.79, P 〉0.05）after CRD. There was no tissue injury or inflammation in distal colon both in MS and control groups before and after CRD. Conclusion Prior neonatal maternal separation stress predisposes rats to exaggerated neurochemical responses and visceral hyperalgesia in adulthood without inducing structural alterations in colon, which mimic the features of visceral hypersensitivity in irritable bowel syndrome, and SP and its NK1 receptor may be not involved in the process.