腹泻型肠易激综合征模型大鼠结肠黏膜下神经丛神经元的改变

The morphological changes of colonic submucosal plexus in rats of irritable bowel syndrome with diarrhea

目的检测慢急性联合应激腹泻型肠易激综合征（IBS-D）模型大鼠结肠黏膜下神经丛（SMP）神经元总数以及特异性标志物阳性神经元的变化，从肠神经系统（ENS）水平推断神经元改变在肠易激综合征（IBS）发病中的作用。方法建立慢急性联合应激IBS-D大鼠模型，留取大鼠结肠制作SMP全层铺片标本。应用免疫组织荧光双染法检测SMP中神经元总数以及乙酰胆碱转移酶（ChAT）、血管活性肠肽（VIP）和一氧化氮合酶（NOS）阳性神经元数目和比例，评价IBS-D模型大鼠ENS神经元的改变。结果IBS-D模型大鼠结肠SMP神经节和神经元总数无明显改变。与对照组相比，IBS-D模型大鼠结肠SMP中VIP阳性神经元比例明显增高（62．2％±6．2％比55．4％±5．4％，P〈0．05），NOS阳性神经元比例亦明显增高（15．0％±4．0％比10．5％±2．9％，P〈0．05），ChAT阳性神经元比例无明显改变。结论IBS-D模型大鼠结肠SMP中VIP阳性神经元和NOS阳性神经元比例增高，提示在慢急性联合应激诱发IBS—D时，ENS中SMP神经元的变化可能通过增加肠道分泌而导致或加重腹泻症状。

Objective To investigate the morphological responses of enteric nervous system （ENS） neurons of submucosal plexus （SMP） in distal colon of rat models with irritable bowel syndrome with diarrhea （IBS-D）. Methods Rat models with IBS-D were established with chronic unpredictable mild stress and acute wrap restrain stress （ CAS ）. Double staining with immunohistofluorescence for colonic whole mount preparations was used to evaluate the distribution and proportion of SMP neurons expressing specific neurochemical markers [choline acetyltransferase （CHAT）, vasoactive intestinal polypeptide （VIP）, and nitric oxide synthase （NOS）] and their coloealization with anti Hu antibody, which is the hallmark for whole enteric neurons. Results There was no obvious difference in the total numbers of anti-Hu positive neurons and ganglia between IBS-D and control group. The proportions of both VIP-immunoreactive （VIP-IR） and NOS-IR neurons in colonic SMP were higher in IBS-D rats compared with controls （62.20% ± 6.2 %vs 55.4% ± 5.4%; 15.0%±4.0% vs 10.5%±2.9%,P〈0.05）. There was no difference in the proportion of ChAT-IR neurons between two groups. Conclusions VIP is the most specific neurotransmitter for excitatory secretomotor neurons in rat SMP, the increase of VIP-IR neurons can promote intestinal mucosal secretion, which might play an important role in the pathophysiological mechanisms of IBS with diarrhea.