Ion channel analysis of neurons of the mesencephalic trigeminal nucleus in in vitro preparations

三叉神经中脑核(MTN)内有两种功能神经元，一种供应闭口肌的肌梭，另一种供应牙周机械感受器，还有两种解剖类型：假单极和多极。本研究的目的是研究在体外制备的每种类型的MTN神经元上离子通道的组织结构。为了实现这一目标，我开发了两种体外制备方法：脑片制备和分离的脑干-脊髓制备。虽然切片制备对离子通道的分析是有用的，但它不能实现单个细胞的表征和系统分析。另一方面，分离的脑干-脊髓准备涉及包括MTN神经元在内的完整回路，并产生反射反应和节律性活动。用负压电极监测三叉神经感觉(Vs)、三叉神经运动(Vm)、舌下神经(Xll)和颈髓前根(C4~C5)的神经活动。结果表明：(1)电刺激Vm和Xll可诱发Vm和Xll的神经抽动；(2)在Vm、Xll和C4，5神经上可观察到不同于记录到的自发呼吸活动的节律性神经放电。目前，我正在尝试分析MTN神经元在这些准备过程中的离子通道机制。

In the trigeminal mesencephalic nucleus (MTN), there are two functional types of neurons : one supplying the muscle spindles in jaw-closing muscles and the other the periodontal mechanoreceptors, and also two anatomical types of neurons : pseudomonopolar and multipolar. The purpose of this study was to investigate the organization of ion-channels on each type of MTN neurons in in vitro preparations.To achieve this goal, I had developed two types of in vitro preparations : slice preparation and isolated brainstem-spinal cord preparation. Although the slice preparation is of use to an analysis of ion-channels, it will not achieve characterizations of individual cells and a system analysis. On the other hand, the isolated brainstem-spinal cord preparation involves intact circuits including MTN neurons and generates reflex responses and rhythmical activity.The in vitro brainster-spinal cord preparation were isolated from neonatal rats (from 0- to 3-day-old). Neural activities were monitored in trigeminal sensory (Vs), trigeminal motor (Vm), hypoglossal (Xll) nerves as well as ventral roots of the cervical spinal cord (C4-C5) with suction electrodes. The following results were obtained : (1) electrical stimulation of Vs evoked nerve volley in Vm and Xll ; (2) rhythmical nerve discharges distinct from spontaneously generated respiratory activities recorded in Vm, Xll and C4,5 nerves could be observed in the Xll nerve after application of N-menthyl-D-aspartate into the bath solution.I conclude that this isolated brainstem-spinal cord preparation will be useful for the investigation of cellular mechanisms (ion-channel) and neuronal organization (system) related to the function of MTN neurons. At present, I am trying to analyze ion-channel mechanisms of MTN neurons in these preparations.