Mechanism of nervous interaction between the enteric nervous system and the autonomic nervous system

本课题旨在研究豚鼠胃、小肠、远端结肠和直肠的肌间神经丛与胃肠道这些部分的外源性自主神经支配之间的突触关系。为了实现这一最终目标，采取了两个实验步骤。作为第一步，用荧光黄或神经生物素对胃或远端结肠肌间神经元进行细胞内染色，以表征细胞形态。在远端结肠中鉴定出两种形态学细胞类型。一种是长突神经元（SLP）和短突神经元（MLP），前者胞体呈椭圆形，表面光滑，有或无短突。MLP神经元的电特性始终是AH/II型神经元的电特性，而SLP神经元则表现出AH/2型、S/typo 1型、单棘波和3型神经元的电特性。在胃肌间神经丛，没有发现MLP神经元，所有的神经元都表现出短的锋电位时程。在该项目的下一步中，从胃和远端结肠肌间神经元进行细胞内记录，同时在细胞外刺激迷走神经和骨盆神经。外源性神经刺激诱发的突触电位仅为长时间延迟的快速兴奋性突触后电位（fast-EPSP）。胃和远端结肠肌间神经丛均无慢突触传入。在结肠肌间神经丛中，快-EPSPs只存在于SLP神经元中，其放电持续时间短于MLP神经元。从中枢神经系统到肌间神经丛的外源性兴奋性输入，似乎是由C纤维以快-EPSP的形式介导的，而只介导到SLP神经元。

This project has been designed to investigate the synaptic relationships between the myenteric plexus in the guinea pig stomach, small intestine, distal colon and rectum and the extrinsic autonomic innervations to these parts of the gastrointestinal tract. In order to address this final target, two experimental steps have been made. As a first step, stomach or distal colonic myenteric neurons were stained intracellularly with Lucifer yellow or neurobiotin to Characterize the cellular morphology. Two morphological cell types were identified in the distal colon. One was neurons with a single long process (SLP) and multiple short processes in various forms and the other was neuron which had multiple long process (MLP) emanating a oval smooth surfaced cell body with or without short processes. Electrical properties of MLP neurons were always those of the AH/type II neurons but SLP neurons showed various characteristics those of including AH/type 2, S/typo 1, Single spike and Type 3 neurons. In the stomach myenteric plexus, no MLP neuron was found and all of the neurons showed short spike durations. In the next step of the project, intracellular recordings were made from stomach and distal colonic myenteric neurons while vagus and pelvic nerves were stimulated extracellularly. Synaptic potentials evoked by extrinsic nerve stimulations were only fast excitatory postsynatpic potentials (fast-EPSPs) with long time delays. No slow synaptic input was found either stomach or distal colonic myenteric plexus. In the colonic myenteric plexus fast-EPSPs were found only in the SLP neurons which had shorter spike duration than MLP neurons. It appeared that extrinsic excitatory inputs from central nervous system to the myenteric plexus were medicated by C fibers in the form of fast-EPSPs and only to the SLP neurons.