Morphology and physiology of masticatory neurons in the trigeminal principal nucleus and supratrigemenal nucleus -intracellular recording and HRP injection technique-

虽然主核（Vp）包含三叉丘脑和核间束细胞，但两种神经元在功能和形态上的差异尚不清楚。本研究旨在通过猫细胞内辣根过氧化物酶（HRP）注射技术来解决这些问题。在染色的20个神经元中，7个和13个分别位于Vp的背内侧亚核（Vpd）和腹外侧亚核（Vpv）。Vpd神经元只接受来自口内结构的输入，Vpv神经元则接受来自口内或面部结构的输入。19个神经元根据其干轴突的分支方式可分为ⅰ类和ⅱ类，ⅰ类神经元（8个）有一个上行的干轴突而无分支，ⅱ类神经元分为IIa和IIb两个亚类。IIa类（8个神经元）有一个上升的茎轴突，分支从茎轴突上发出。它们的分支形成了局限于脑干下部的局部回路，IIb类（3个神经元）的茎轴突只形成了局部回路。树突形态在神经元的不同类别和细分之间难以区分。虽然树突状树突的分布模式是由躯体的位置决定的，但它也被认为是决定初级传入树突的重要因素。在脑干核中，闭颌运动核接收到的ⅱ类神经元的投射密度最高，其感受野涉及牙周韧带。本研究提供了新的发现，Vp神经元可以分为三个不同的群体，并表明每个群体在感觉辨别和/或感觉运动反射方面发挥不同的功能。

Although the principalis nucleus (Vp) contains trigeminothalamic and internuclear tract cells, the functional and morphological differences between the two kinds of neurons have remained unsettled.The present study was aimed to address these problems by using the intracellular horseradish peroxidase (HRP) injection technique in the cat.Of 20 neurons stained, seven and thirteen were located in the dorsomedial subnucleus (Vpd) and ventrolateral subnucleus (Vpv) of Vp, respectively.The Vpd neurons received input from the intraoral structures only but the Vpv neurons from the intraoral or facial structures.Nineteen neurons could be divided as class I and class II, based on the branching pattern of their stem axons Class I (eight neurons) had an ascending stem axon without branching.Class II was divided into two subclasses (IIa and IIb). Class IIa (eight neurons) had an ascending stem axon from which branches were given off.Their branches formed a local-circuit restricted to the lower brainstem.Class IIb (three neurons) had a stem axon that formed the local-circuit only.The dendritic morphology was indistinguishable between different classes of neurons and between the subdivisions.Although the dendritic arborization pattern was governed by the location of the somata, it was suggested to be also important elements for determining primary affrent arborizations.In the brainstem nuclei, the jaw-closing motor nucleus received the highest density of projections from class II neurons with the receptive field involving the periodontal ligaments.The present study provided new findings that Vp neurons could be divided into three distinct populations, and suggests that each population exerts a distinct function with respect to sensory discrimination and/or sensorimotor reflexes.