Pickel V M, Chan J
Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021.
Neuroscience. 1991;41(2-3):459-72. doi: 10.1016/0306-4522(91)90341-k.
We have observed that in rat caudate-putamen nuclei, neurons immunolabeled for choline acetyltransferase were sometimes in direct apposition to unlabeled perikarya and dendrites [Pickel V. M. and Chan J. (1990) J. Neurosci. Res. 25, 263-280]. Similar juxtapositions between plasmalemmas of nerve cells each receiving input from one common terminal have been associated with activation of certain central neurons [Theodosis D. T. and Poulain D. A. (1989) Brain Res. 484, 361-366]. Thus, we sought to determine the relative abundance and ultrastructure of the appositions and the frequencies of shared synapses between choline acetyltransferase-labeled and unlabeled neurons in the rat striatum. A monoclonal antibody raised against choline acetyltransferase was localized in semi-adjacent ultrathin sections through 24 neurons in the dorsolateral caudate-putamen nuclei. Five of these choline acetyltransferase-labeled perikarya showed direct somatic appositions with unlabeled neurons. The remaining 19 of the choline acetyltransferase-labeled perikarya did not show somatic appositions with unlabeled perikarya; however, when traced through multiple (20-100) semi-adjacent sections their dendrites always showed extensive plasmalemmal juxtapositions with one or more unlabeled perikarya. The apposed perikarya had round nuclei and other characteristics of medium, spiny neurons. The majority of the apposed cholinergic and non-cholinergic neurons were postsynaptic to at least one common unlabeled terminal. These terminals usually formed symmetric junctions. At sites of appositions, the plasmalemmas of choline acetyltransferase-immunoreactive soma or dendrites and unlabeled neurons were closely spaced without intervening astrocytic processes. The appositions lacked the ultrastructural features typical of gap-junctions, but did occasionally show parallel arrays of thin (1-2 nm) electron-dense bands. In both labeled and unlabeled perikarya, the nuclei were separated from the appositional zones by narrow (0.7-3.3 microns) rims of cytoplasm. This cytoplasmic rim contained subsurface cisternae and other less specialized smooth and rough endoplasmic reticulum, and vesicular structures. The findings suggest that in the caudate-putamen nuclei (1) the tonically active cholinergic neurons [Wilson C. J. et al. (1990) J. Neurosci. 10, 508-519] may modulate or be modulated by non-cholinergic spiny neurons through non-synaptic somatic or dendritic appositions, and (2) that both neurons may be simultaneously inhibited by shared afferent input. Activation of this system could facilitate coordinated movements through synchronization of cholinergic interneurons and spiny projection neurons containing GABA or other transmitters.
我们观察到，在大鼠尾状核-壳核中，胆碱乙酰转移酶免疫标记的神经元有时与未标记的胞体和树突直接并置[皮克尔V.M.和陈J.（1990年）《神经科学研究杂志》25卷，263 - 280页]。每个从一个共同终末接受输入的神经细胞质膜之间的类似并置情况，已与某些中枢神经元的激活相关联[西奥多西斯D.T.和普兰D.A.（1989年）《脑研究》484卷，361 - 366页]。因此，我们试图确定大鼠纹状体中胆碱乙酰转移酶标记和未标记神经元之间并置的相对丰度和超微结构以及共享突触的频率。一种针对胆碱乙酰转移酶产生的单克隆抗体，通过背外侧尾状核-壳核中的24个神经元定位在半相邻超薄切片中。这些胆碱乙酰转移酶标记的胞体中有5个显示与未标记神经元有直接的体细胞并置。其余19个胆碱乙酰转移酶标记的胞体未显示与未标记胞体有体细胞并置；然而，当通过多个（20 - 100个）半相邻切片追踪时，它们的树突总是显示与一个或多个未标记胞体有广泛的质膜并置。并置的胞体有圆形细胞核以及中型有棘神经元的其他特征。大多数并置的胆碱能和非胆碱能神经元至少有一个共同的未标记终末作为突触后神经元。这些终末通常形成对称连接。在并置部位，胆碱乙酰转移酶免疫反应性胞体或树突与未标记神经元的质膜紧密间隔，没有中间的星形胶质细胞突起。这些并置缺乏典型的缝隙连接超微结构特征，但偶尔会显示平行排列的薄（1 - 2纳米）电子致密带。在标记和未标记的胞体中，细胞核通过狭窄（0.7 - 3.3微米）的细胞质边缘与并置区域分隔开。这个细胞质边缘包含表面下池以及其他不太特化的光滑和粗糙内质网，还有囊泡结构。这些发现表明，在尾状核-壳核中：（1）持续活跃的胆碱能神经元[威尔逊C.J.等人（1990年）《神经科学杂志》10卷，508 - 519页]可能通过非突触性体细胞或树突并置调节非胆碱能有棘神经元或被其调节；（2）这两种神经元可能同时被共享的传入输入抑制。该系统的激活可能通过胆碱能中间神经元与含有γ-氨基丁酸或其他递质的有棘投射神经元的同步化来促进协调运动。
