Poole Daniel P, Xu Bo, Koh Shir Lin, Hunne Billie, Coupar Ian M, Irving Helen R, Shinjo Katsuhiro, Furness John B
Department of Anatomy & Cell Biology and Centre for Neuroscience, University of Melbourne, Parkville 3010, Australia.
Cell Tissue Res. 2006 Sep;325(3):413-22. doi: 10.1007/s00441-006-0181-9. Epub 2006 Apr 21.
5-Hydroxytryptamine (5-HT) is an endogenous stimulant of intestinal propulsive reflexes. It exerts its effects partly through 5-HT4 receptors; 5-HT4 receptor agonists that are stimulants of intestinal transit are in clinical use. Both pharmacological and recent immunohistochemical studies indicate that 5-HT4 receptors are present on enteric neurons but the specific neurons that express the receptors have not been determined. In the present work, we describe the characterization of an anti-5-HT4 receptor antiserum that reveals immunoreactivity for enteric neurons and other cell types in the gastrointestinal tract. With this antiserum, 5-HT4 receptor immunoreactivity has been found in the muscularis mucosae of the rat oesophagus, a standard assay tissue for 5-HT4 receptors. It is also present in the muscularis mucosae of the guinea-pig and mouse oesophagus. In guinea-pig small intestine and rat and mouse colon, 5-HT4 receptor immunoreactivity occurs in subpopulations of enteric neurons, including prominent large neurons. Double-staining has shown that these large neurons in the guinea-pig small intestine are also immunoreactive for two markers of intrinsic primary afferent neurons, cytoplasmic NeuN and calbindin. Some muscle motor neurons in the myenteric ganglia are immunoreactive for this receptor, whereas it is rarely expressed by secretomotor neurons. Immunoreactivity also occurs in the interstitial cells of Cajal but is faint in the external muscle. Expression of the protein and mRNA has been confirmed in extracts containing enteric neurons. The observations suggest that one site of action of 5-HT4 receptor agonists is the intrinsic primary afferent neurons.
5-羟色胺（5-HT）是肠道推进反射的内源性刺激物。它部分通过5-HT4受体发挥作用；作为肠道转运刺激物的5-HT4受体激动剂正在临床应用。药理学研究和近期的免疫组织化学研究均表明，5-HT4受体存在于肠神经元上，但表达该受体的具体神经元尚未确定。在本研究中，我们描述了一种抗5-HT4受体抗血清的特性，该抗血清可显示胃肠道中肠神经元和其他细胞类型的免疫反应性。利用这种抗血清，在大鼠食管的黏膜肌层中发现了5-HT4受体免疫反应性，大鼠食管是检测5-HT4受体的标准组织。在豚鼠和小鼠食管的黏膜肌层中也存在这种免疫反应性。在豚鼠小肠以及大鼠和小鼠结肠中，5-HT4受体免疫反应性出现在肠神经元亚群中，包括突出的大神经元。双重染色显示，豚鼠小肠中的这些大神经元对两种内在初级传入神经元标志物——细胞质NeuN和钙结合蛋白也具有免疫反应性。肌间神经节中的一些肌肉运动神经元对该受体具有免疫反应性，而分泌运动神经元很少表达该受体。免疫反应性在Cajal间质细胞中也存在，但在外部肌肉中很微弱。在含有肠神经元的提取物中已证实了该蛋白和mRNA的表达。这些观察结果表明，5-HT4受体激动剂的一个作用位点是内在初级传入神经元。
