Enteric Dysfunctions in Experimental Parkinson's Disease: Alterations of Excitatory Cholinergic Neurotransmission Regulating Colonic Motility in Rats
Enteric Dysfunctions in Experimental Parkinson's Disease: Alterations of Excitatory Cholinergic Neurotransmission Regulating Colonic Motility in Rats
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DOI：
10.1124/jpet.115.228510
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发表时间：
2016-02-01
影响因子：
3.5
通讯作者：
Colucci, Rocchina
中科院分区：
文献类型：
--
作者：
Fornai, Matteo;Pellegrini, Carolina;Colucci, Rocchina
帕金森氏症经常与胃肠道症状有关，主要表现为便秘和排便功能障碍。本研究观察了前脑束内侧注射6-羟基多巴胺(6-OHDA)所致的中枢多巴胺能去神经支配对大鼠结肠远端兴奋性胆碱能神经运动活动的影响。分别于注射6-OHDA后4周和8周处死动物。用放射学方法评价体内结肠运输情况。电诱导和氨基甲胆碱诱导的胆碱能收缩在体外从纵行和环行结肠组织中记录下来，而乙酰胆碱水平则在孵育介质中被检测。用免疫组织化学法或免疫印迹法检测胆碱乙酰转移酶(ChAT)、泛神经元标志物Huc/D、M受体M2和M3的表达。与对照组相比，4周时，6-OHDA处理组大鼠的结肠传输速度降低，电诱发的神经源性胆碱能收缩减弱，氨基甲胆碱诱发的收缩增强，基础和电刺激的乙酰胆碱释放减少，神经肌肉层ChAT免疫阳性反应降低，Huc/D免疫反应阳性肌间神经元密度不变，结肠M_2和M_3受体表达增加。大多数这种改变也是在注射6-OHDA后第8周检测到的。这些结果表明，中枢黑质纹状体多巴胺能去神经与兴奋性神经传递受损有关，表现为肌间神经元ChAT阳性丢失和乙酰胆碱释放减少，导致平滑肌运动活动失调，这可能是导致结肠传输率下降的原因之一。
Parkinson's disease is frequently associated with gastrointestinal symptoms, mostly represented by constipation and defecatory dysfunctions. This study examined the impact of central dopaminergic denervation, induced by injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle, on distal colonic excitatory cholinergic neuromotor activity in rats. Animals were euthanized 4 and 8 weeks after 6-OHDA injection. In vivo colonic transit was evaluated by radiologic assay. Electrically induced and carbachol-induced cholinergic contractions were recorded in vitro from longitudinal and circular muscle colonic preparations, whereas acetylcholine levels were assayed in the incubation media. Choline acetyltransferase (ChAT), HuC/D (pan-neuronal marker), muscarinic M2 and M3 receptors were assessed by immunohistochemistry or western blot assay. As compared with control rats, at week 4, 6-OHDA-treated animals displayed the following changes: decreased in vivo colonic transit rate, impaired electrically evoked neurogenic cholinergic contractions, enhanced carbachol-induced contractions, decreased basal and electrically stimulated acetylcholine release from colonic tissues, decreased ChAT immunopositivity in the neuromuscular layer, unchanged density of HuC/D immunoreactive myenteric neurons, and increased expression of colonic muscarinic M2 and M3 receptors. The majority of such alterations were also detected at week 8 post 6-OHDA injection. These findings indicate that central nigrostriatal dopaminergic denervation is associated with an impaired excitatory neurotransmission characterized by a loss of myenteric neuronal ChAT positivity and decrease in acetylcholine release, resulting in a dysregulated smooth muscle motor activity, which likely contributes to the concomitant decrease in colonic transit rate.