新生期结直肠扩张对发育期大鼠内脏痛觉敏感性影响

Effect of neonatal colorectal distention on visceral sensibility of pain in developing rats

目的探讨新生期伤害性结直肠扩张刺激(CRD)对发育期大鼠内脏痛觉敏感性的影响。方法8日龄新生SD大鼠随机分成实验组和对照组,每组16只;实验组新生鼠在出生第8天开始给予结直肠刺激,1次/d,连续7d;对照组则不给予结直肠刺激。随后,两组大鼠常规饲养到6周龄时进行内脏敏感性测定。采用腹壁撤退反射(AWR)评分和痛阈测定作为不同的扩张压力下结直肠疼痛反应指标,评估肠道痛觉敏感性。采用单因素和重复测量方差分析进行统计学分析,α=0.05为显著性检验标准。结果6周时两组大鼠体重差异无统计学意义;两组大鼠降结肠均未见明显病理组织损伤;随CRD压力增加,两组幼鼠AWR评分增加,实验组幼鼠CRD在60mmHg和80mmHg之间评分差异无统计学意义;在20、40、60mmHg范围内,相同压力下,实验组幼鼠评分明显高于对照组,差异有统计学意义,当CRD压力为80mmHg时,两组评分差异无统计学意义;实验组和对照组大鼠痛阈值分别为26.5±4.9mmHg、47.8±5.0mmHg,两组痛阈差异有统计学意义(F=149.753,P<0.01)。结论新生期进行持续的结直肠刺激的确能造成大鼠痛阈下降,出现慢性内脏高敏感性,并且这种高敏感性能持续到幼年期,同时无明显的组织学改变。

Objective To study the effect of detrimental colorectal distention （CRD） stimulation in neonatal period on visceral sensibility of pain in developing rats. Methods Eight day old Sprague- Dawley rats were divided randomly into experimental group （n = 16） and control group （n = 16）. Rats in experimental group were treated with colorectal distension once a day for 7 consecutive days and rats in control group were not treated. On the 6th week, the visceral sensitivity of all rats was evaluated. The abdominal withdrawal reflex （AWR） and pain thresholds which were used as pain responding indicators were measured to evaluate the bowel sensitivity. Biopsy of descending colon was done for histopatholigical studies. One-way and repeated measuring ANOVA were used to analyze differences between the two groups. Results There were no significant differences of weight between the two groups and there were no significant histopatholigical changes in the gross and microscopic studies of descending colon observed when the rats were 6 weeks old. The AWR score increased gradually with the rising of the CRD pressures in both groups. But there was no significantly different of the AWR score when the CRD pressure roused from 60 to 80mmHg in the experimental group. When the CRD pressure ranged from 20 to 60 mm Hg, the AWR scores was higher in the experimental group than the control. But when pressure reached 80mmHg, there was no significant difference of AWR scores between two groups. The pain threshold was significantly different in experimental and control group, （26. 5 ±4. 9 ） mm Hg vs. （47.8 ± 5.0 ） mm Hg, F = 149. 753 ,P 〈0. 01. Conclusions The persistent stimulation of CRD in neonatal phase results in decreasing of pain threshold and increasing of chronic visceral sensibility. The hyperalgesia can continue to juvenile stage and there is no histological change found in colorectal tissues.