帕金森病模型大鼠结肠电-机械活动的改变

目的探讨帕金森病(Parkinson’s disease,PD)大鼠模型结肠功能紊乱与结肠电-机械活动、神经型一氧化氮合酶(nNOS)和胃肠调节肽之间的关系。方法以6-羟多巴胺(6-hydroxydopamine,6-OHDA)诱导制备实验性帕金森病大鼠模型,并用左旋多巴(levodopa)处理正常大鼠和模型鼠,记录其结肠电-机械活动,观察PD和左旋多巴对结肠电-机械活动的影响。采用免疫组织化学方法观察结肠肌间神经丛nNOS和血管活性肠肽(VIP)以及酪氨酸羟化酶(TH)的变化,并用Western blotting法定量检测TH在结肠肌间神经丛的表达。结果1)与正常对照组比较,未接受左旋多巴治疗的PD组大鼠模型的结肠慢波峰值频率明显降低,差异有统计学意义(P<0.05),正常慢波百分比明显降低,差异有统计学意义(P<0.05),运动平均振幅明显降低,差异有统计学意义(P<0.05)。2)与正常对照组比较,左旋多巴组结肠慢波峰值频率呈增高趋势,但差异无统计学意义,运动峰值频率明显增高,差异有统计学意义(P<0.05)。3)与正常对照组比较,PD+左旋多巴组运动峰值频率明显增高,差异有统计学意义(P<0.05),运动平均振幅明显降低,差异有统计学意义(P<0.05),正常慢波百分比明显降低,差异有统计学意义(P<0.05)。4)PD组和PD+左旋多巴组结肠肌间神经丛表达nNOS的神经元个数明显增加(P<0.05),灰度值明显降低(P<0.05)。5)各组结肠黏膜下神经丛VIP未发现有异常改变。6)PD组TH染色阳性的神经元显著减少,差异有统计学意义(P<0.05),TH的蛋白表达降低。结论NO能神经元可能参与PD结肠活动的抑制过程,而VIP能神经元可能并未参与PD结肠活动的调节。PD还可能造成胃肠道多巴胺能神经元的缺陷,多巴胺能神经元减少对于PD结肠功能障碍也可能起一定作用。

Changes of the Colon Electro-mechanical Activity in the Rat Model of Parkinson's Disease

Objective To investigate the relationship of the colon dysfunction to electromechanical activity, the expression of neuronal nitric oxide synthase(nNOS) and gastrointestinal regulation peptides in colon of patients with Parkinson's disease. Methods The colon smooth muscle contractility and basic electrical rhythm following 6-hydroxydopamine(6-OHDA) induced neurodegeneration were studied in rats. In the mean time, the Parkinson disease model rats and normal rats were treated with levodopa. Immunohistochemistry was used to stain myenteric and submucosal neurons for nNOS and vasoactive intestinal polypeptide(VIP) and tyrosine hydroxylase(TH) in colon tissues. In addition, Western blotting was used to analyze the expression of TH in colon tissues. Results 1 In untreated PD group, the dominant frequency of slow wave and the percentage of normal slow wave in colon significantly decreased(P<0.05). In addition, the average amplitude of colon contraction also obviously decreased(P<0.05). 2 In levodopa group, the dominant frequency of slow wave in colon increased. And the dominant frequency of contraction significantly increased(P<0.05). 3 The levodopa treated PD group also showed significant increase in the dominant frequency of contraction in colon(P<0.05). However, the average amplitude of contraction and the percentage of normal slow wave in colon significantly decreased(P<0.05). 4 An increase in the intensity of immunoreactivity for nNOS(P<0.05) as well as an increase in the number of nNOS-positive cells were found in the myenteric plexus in untreated PD group and levodopa treated PD group(P<0.05). 5 No significant difference was found among the groups in numbers of VIP neurons in submucosal plexus. 6 Compared with the control group, the TH-positive neurons in the myenteric plexus in untreated PD group significantly decreased(P<0.05). Conclusion PD had directly negative effects on myoelectrical activity in colon. It may influence the colon motility by the decrease of the frequency of slow wave and the smooth muscle contractility. These changes may play an important role in development of constipation. Levodopa had an excitatory effect on colon motility. An excessive production of nitric oxide may cause the inhibition of motility in colon. VIP neurons may not be involved in modulating the colon motility in PD. The decrease of dopaminergic neurons may be responsible for the dysfunction of colon in PD.