Balercia G, Kultas-Ilinsky K, Bentivoglio M, Ilinsky I A
Institute of Anatomy and Histology, University of Verona, Italy.
J Neurocytol. 1996 Apr;25(4):267-88. doi: 10.1007/BF02284802.
The ultrastructure of the centromedian nucleus of the monkey thalamus was analysed qualitatively and quantitatively and projection neurons, local circuit neurons, and synaptic bouton populations identified. Projection neurons were mostly medium-sized, with oval-fusiform or polygonal perikarya, few primary dendrites, and frequent somatic spines; local circuit neurons were smaller. Four basic types of synaptic boutons were distinguished: (1) Small- to medium-sized boutons containing round vesicles (SR) and forming asymmetric contacts, identified as corticothalamic terminals. (2) Heterogeneous medium-sized boutons with asymmetric contacts and round vesicles, similar to the so-called large round (LR) boutons, which were in part of cortical origin. (3) Heterogeneous GAD-positive small- to medium-sized boutons, containing pleomorphic vesicles and forming symmetric contacts (F1 type), which included pallidothalamic terminals. (4) Presynaptic profiles represented by GAD-positive vesicle-containing dendrites of local circuit neurons. Complex synaptic arrangements, serial synapses and triads with LR and SR boutons engaging all parts of projection neuron dendrites and somata, were seen consistently, whereas classical glomeruli were infrequent. LR and SR boutons also established synapses on dendrites of local circuit neurons. F1 boutons established synapses on projection neuron somata, dendrites and initial axon segments. Compared to other previously studied motor-related thalamic nuclei, differences in synaptic coverage between proximal and distal projection neuron dendrites were less pronounced, and the density of synapses formed by local circuit dendrites on projection neuron dendrites was lower. Thus, compared to other thalamic nuclei, the overlap of different inputs was higher on monkey centromedian cells, and centromedian inhibitory circuits displayed a different organization.
对猴丘脑中央中核的超微结构进行了定性和定量分析，并识别出投射神经元、局部回路神经元和突触小体群体。投射神经元大多为中等大小，胞体呈椭圆形梭形或多边形，初级树突较少，体细胞棘突常见；局部回路神经元较小。区分出四种基本类型的突触小体：(1) 含有圆形囊泡（SR）并形成不对称接触的中小型突触小体，被鉴定为皮质丘脑终末。(2) 具有不对称接触和圆形囊泡的异质性中等大小突触小体，类似于所谓的大圆形（LR）突触小体，部分起源于皮质。(3) 异质性GAD阳性的中小型突触小体，含有多形性囊泡并形成对称接触（F1型），包括苍白球丘脑终末。(4) 以局部回路神经元含GAD阳性囊泡的树突为代表的突触前轮廓。始终可见复杂的突触排列、串联突触以及LR和SR突触小体与投射神经元树突和胞体各部分形成的三联体，而经典的小球体则很少见。LR和SR突触小体也在局部回路神经元的树突上建立突触。F1突触小体在投射神经元的胞体、树突和轴突起始段建立突触。与其他先前研究的运动相关丘脑核相比，投射神经元近端和远端树突之间的突触覆盖差异不太明显，局部回路树突在投射神经元树突上形成的突触密度较低。因此，与其他丘脑核相比，不同输入在猴中央中核细胞上的重叠更高，并且中央中核抑制性回路表现出不同的组织形式。
