Behan M, Appell P P, Graper M J
Department of Comparative Biosciences, University of Wisconsin, Madison 53706.
J Comp Neurol. 1988 Apr 8;270(2):171-84. doi: 10.1002/cne.902700203.
The ultrastructure of large neurons in the stratum griseum intermedium of the cat superior colliculus was examined following injections of horseradish peroxidase (HRP) into the dorsal tegmental decussation. Four HRP-labeled cells were selected, and the synaptology of their cell bodies and selected regions of proximal and distal dendrites was examined. The four neurons represent four morphologically distinct cell types: multipolar radiating, tufted, large vertical, and medium-sized trapezoid radiating. These four neurons correspond with cell types X1, X2, X3, and T1 respectively, according to the recent classification of neurons in the superior colliculus of the cat by Moschovakis and Karabelas (J. Comp Neurol. 239:276-308, '85). The three X type neurons are similar in having 83% of their somata and over 74% of their proximal dendrites contacted by synaptic profiles. Distal dendrites of the X type neurons, however, receive fewer synaptic contacts. In contrast, in the T1 cell, only 69% of the soma membrane is contacted by synaptic profiles, and the synaptic coverage on proximal and distal dendrites does not vary much from this. Of the eight types of synaptic terminals described in the stratum griseum intermedium of the cat superior colliculus by Norita (J. Comp. Neurol. 190:29-48, '80), only five are found in contact with the X and T type efferent neurons described here. There are some regional differences in terminal distribution, although each terminal is represented on each cell. Type III terminals (small, contain mostly pleomorphic vesicles, and make symmetrical contacts) are the most abundant on cell bodies and dendrites of all four cell types. Terminal types II (medium-sized, containing round and flattened vesicles, and making asymmetrical contacts), and IV (medium to large in size, containing flattened vesicles, and making symmetrical contacts) are well represented. In general, terminal types I (small, containing densely packed round vesicles, and making asymmetrical contacts) and VI (small and irregular in shape, containing flattened vesicles and making symmetrical contacts) are found infrequently. The identity of different types of synaptic terminal is discussed.
将辣根过氧化物酶（HRP）注入猫上丘中间灰质层后，对其中大神经元的超微结构进行了研究。选取了4个HRP标记的细胞，并对其胞体以及近端和远端树突的选定区域的突触学进行了研究。这4个神经元代表4种形态上不同的细胞类型：多极放射状、簇状、大垂直状和中等大小的梯形放射状。根据Moschovakis和Karabelas（《比较神经学杂志》239:276 - 308，'85）最近对猫上丘神经元的分类，这4个神经元分别对应X1、X2、X3和T1细胞类型。3种X型神经元的相似之处在于，它们83%的胞体和超过74%的近端树突被突触轮廓所接触。然而，X型神经元的远端树突接受的突触接触较少。相比之下，在T1细胞中，只有69%的胞体膜被突触轮廓所接触，并且近端和远端树突上的突触覆盖与胞体膜上的差异不大。Norita（《比较神经学杂志》190:29 - 48，'80）描述的猫上丘中间灰质层中的8种突触终末类型中，只有5种与这里描述的X型和T型传出神经元接触。虽然每个终末类型在每个细胞上都有表现，但终末分布存在一些区域差异。III型终末（小，大多含有多形性囊泡，并形成对称接触）在所有4种细胞类型的胞体和树突上最为丰富。II型终末（中等大小，含有圆形和平扁囊泡，并形成不对称接触）和IV型终末（中等至大，含有扁囊泡，并形成对称接触）也有很好的表现。一般来说，I型终末（小，含有密集排列的圆形囊泡，并形成不对称接触）和VI型终末（小且形状不规则，含有扁囊泡并形成对称接触）很少见。文中讨论了不同类型突触终末的特征。
