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

本项目旨在研究豚鼠胃、小肠、远端结肠和直肠的肌肠丛与胃肠道这些部位的外在自主神经支配之间的突触关系。为了实现这一最终目标，我们采取了两个实验步骤。第一步，用路西法黄或神经生物素对胃或结肠远端肌肠神经元进行细胞内染色，以表征细胞形态。在远端结肠中发现两种形态细胞类型。一种是具有单个长过程和多个不同形式的短过程的神经元，另一种是具有多个长过程的神经元，其胞体呈椭圆形光滑表面，有或没有短过程。MLP神经元的电特性与AH/ II型神经元相同，而SLP神经元的电特性则与AH/ 2型、S/ 1型、单峰和3型神经元不同。在胃肌丛中未发现MLP神经元，且所有神经元均呈短峰持续时间。在项目的下一步，从胃和结肠远端肌肠神经元进行细胞内记录，同时在细胞外刺激迷走神经和盆腔神经。外源性神经刺激引起的突触电位仅为长时间延迟的快速兴奋性突触后电位（fast- epsps）。胃或结肠远端肌丛均未发现缓慢的突触输入。在结肠肌肠丛中，快速epsp仅存在于SLP神经元中，且其峰值持续时间比MLP神经元短。从中枢神经系统到肌间丛的外源性兴奋输入似乎是由C纤维以快速epsp的形式给药的，并且只给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.