School of Biomedical Sciences, University of Queensland, St. Lucia, QLD 4072, Australia.
Am J Physiol Lung Cell Mol Physiol. 2010 Mar;298(3):L404-16. doi: 10.1152/ajplung.00166.2009. Epub 2010 Jan 8.
In the present study, we describe a subset of nerve fibers, characterized by their immunoreactivity for the calcium-binding protein calretinin, that are densely and selectively associated with cholinergic postganglionic neurons in the guinea pig tracheal ganglia. Retrograde neuronal tracing with cholera toxin B, combined with immunohistochemical analyses, showed that these nerve fibers do not originate from sensory neurons in the nodose, jugular, or dorsal root ganglia or from motor neurons in the nucleus ambiguus, dorsal motor nucleus of the vagus nerve, spinal cord, stellate ganglia, or superior cervical ganglia. Calretinin-immunoreactive nerve fibers disappeared from tracheal segments after 48 h in organotypic culture, indicating that the fibers were of extrinsic origin. However, calretinin-positive nerve fibers persisted in tracheal ganglia when tracheae were cocultured with the adjacent esophagus intact. Immunohistochemical analysis of the esophagus revealed a population of cholinergic neurons in the esophageal myenteric plexus that coexpressed calretinin. In functional studies, electrical stimulation of the esophagus in vitro evoked measurable contractions of the trachea. These contractions were not altered by prior organotypic culture of the trachea and esophagus to remove the extrinsic innervation to the airways but were significantly (P < 0.05) inhibited by the ganglionic blocker hexamethonium or by physical disruption of the tissue connecting the trachea and esophagus. These data suggest that a subset of esophageal neurons, characterized by the expression of calretinin and acetylcholine, provide a previously unrecognized excitatory input to tracheal cholinergic ganglia in guinea pigs.
在本研究中，我们描述了一组神经纤维亚群，其特征是对钙结合蛋白 calretinin 的免疫反应性，这些纤维与豚鼠气管神经节中的胆碱能节后神经元紧密且选择性地相关。用霍乱毒素 B 进行逆行神经元追踪，结合免疫组织化学分析，表明这些神经纤维并非来自结状神经节、颈静脉神经节或脊神经根中的感觉神经元，也不是来自疑核、迷走神经背核、脊髓、星状神经节或颈上交感神经节中的运动神经元。在器官型培养 48 小时后，气管段中的 calretinin 免疫反应性神经纤维消失，表明这些纤维是外源性的起源。然而，当气管与相邻的食管完整共培养时，calretinin 阳性神经纤维仍存在于气管神经节中。对食管的免疫组织化学分析显示，食管肌间神经丛中存在一群表达 calretinin 的胆碱能神经元。在功能研究中，体外刺激食管可引起气管的可测量收缩。这些收缩不受气管和食管的器官型培养（以去除气道的外源性神经支配）的影响，但被神经节阻滞剂 hexamethonium 或气管和食管之间的组织物理破坏显著抑制（P<0.05）。这些数据表明，一组表达 calretinin 和乙酰胆碱的食管神经元，为豚鼠气管胆碱能神经节提供了以前未被认识的兴奋性输入。
