Shigenaga Yoshio, Bae Yong Chul, Moritani Masayuki, Yoshida Atsushi
Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University, Suita, Osaka 565-0871, Japan.
Arch Oral Biol. 2007 Apr;52(4):321-4. doi: 10.1016/j.archoralbio.2006.11.003. Epub 2006 Dec 15.
This paper reviews recent data on the spatial distribution of inhibitory and excitatory synapses on the dendritic tree of jaw-closing (JC) and -opening (JO) motoneurons in the cat, in which a combination of techniques employing intracellular injections of horseradish peroxidase and postembedding immunogold labelling was used. The dendritic tree is divided into three segments: primary and distal dendrites and intermediate dendrites between the two segments. The proportion of inhibitory boutons (immunoreactive for GABA and/or glycine) is slightly higher than proportion of excitatory boutons (immunoreactive for glutamate) in JC motoneurons, but this trend is reversed in JO motoneurons. In the two kinds of motoneuron, boutons immunoreactive to glycine alone are more numerous than boutons double-labelled to GABA and glycine, which, in turn, occur more frequently than boutons immunoreactive to GABA alone. In JC motoneurons, the packing density (number of boutons per 100 microm(2)) of the inhibitory boutons decreases somatofugally, but this trend is not applicable to the excitatory boutons. In contrast, the packing density of the inhibitory and excitatory boutons in JO motoneurons does not significantly differ among the three dendritic compartments, though it is slightly higher for the excitatory than the inhibitory ones on each dendritic segment. These differences have important implications for synaptic integration in JC and JO motoneurons.
本文综述了有关猫的闭口（JC）和开口（JO）运动神经元树突上抑制性和兴奋性突触空间分布的最新数据，研究中采用了细胞内注射辣根过氧化物酶和包埋后免疫金标记相结合的技术。树突分为三个部分：初级树突、远端树突以及二者之间的中间树突。在JC运动神经元中，抑制性终扣（对γ-氨基丁酸和/或甘氨酸呈免疫反应性）的比例略高于兴奋性终扣（对谷氨酸呈免疫反应性）的比例，但在JO运动神经元中这种趋势则相反。在这两种运动神经元中，仅对甘氨酸呈免疫反应性的终扣比同时对γ-氨基丁酸和甘氨酸呈双重标记的终扣数量更多，而后者又比仅对γ-氨基丁酸呈免疫反应性的终扣出现得更频繁。在JC运动神经元中，抑制性终扣的堆积密度（每100平方微米终扣的数量）沿离胞体方向递减，但这种趋势不适用于兴奋性终扣。相比之下，JO运动神经元中抑制性和兴奋性终扣的堆积密度在三个树突区室之间并无显著差异，尽管在每个树突段上兴奋性终扣的堆积密度略高于抑制性终扣。这些差异对JC和JO运动神经元的突触整合具有重要意义。
