van der Togt C, Nunes Cardozo B, van der Want J
Department of Morphology, The Netherlands Ophthalmic Research Institute, Amsterdam.
J Comp Neurol. 1991 Oct 8;312(2):231-41. doi: 10.1002/cne.903120206.
In this study the medial terminal nucleus (MTN) projection to the nucleus of the optic tract (NOT) was investigated in pigmented rats at the light and electron microscopical levels with a new combination of techniques. MTN terminals were anterogradely labeled with Phaseolus vulgaris-leucoagglutinin (PHA-L). Preembedding immunocytochemistry, followed by gold intensification, was used to visualize PHA-L. Postembedding immunocytochemistry with 15 nm immunogold particles was carried out to demonstrate the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Both PHA-L and GABA labeling can be easily discriminated at the electron microscopical level even when present in the same neuronal profiles. Light microscopically MTN-NOT fibers proved to have several branches with many varicosities. MTN terminals were found concentrated in terminal fields. Electron microscopically, it was shown that MTN boutons display characteristics resembling F-type terminals, i.e., terminals with dark mitochondria, pleomorphic vesicles, and symmetrical synapses. All NOT afferents originating from the MTN contained GABA and made multiple contacts exclusively with GABA negative NOT somata and dendrites. These results indicate the existence of a strong and direct inhibitory input onto GABA negative projection neurons in the NOT. This substantiates earlier physiological and morphological reports. It was further demonstrated that the location and organization of MTN terminals in the neuropil differ from that of the retinal input: MTN terminals are largely separated from retinal terminals. MTN terminal fields contain large amounts of GABA positive F terminals in contrast to retinal terminal areas. MTN terminals take part in irregularly shaped agglomerations of terminals, which contain many F terminals and dendritic processes and are surrounded by a glial sheet. Retinal terminals are found grouped together in small circular arrangements contacting a central dendrite.
在本研究中，运用一组新的技术组合，在光镜和电镜水平上，对有色大鼠内侧终核（MTN）向视束核（NOT）的投射进行了研究。用菜豆白细胞凝集素（PHA-L）对MTN终末进行顺行标记。采用包埋前免疫细胞化学结合金增强技术来显示PHA-L。采用15nm免疫金颗粒进行包埋后免疫细胞化学，以显示抑制性神经递质γ-氨基丁酸（GABA）。即使PHA-L和GABA标记存在于同一神经元形态中，在电镜水平上也很容易区分。光镜下，MTN-NOT纤维有多个分支且有许多曲张。发现MTN终末集中在终末场。电镜显示，MTN终扣具有类似F型终末的特征，即线粒体暗黑、囊泡形态多样且突触对称的终末。所有起源于MTN的NOT传入纤维都含有GABA，且仅与GABA阴性的NOT胞体和树突形成多个接触。这些结果表明，在NOT中，对GABA阴性投射神经元存在强大而直接的抑制性输入。这证实了早期的生理学和形态学报告。进一步证明，MTN终末在神经毡中的位置和组织与视网膜输入不同：MTN终末与视网膜终末在很大程度上是分开的。与视网膜终末区域相比，MTN终末场含有大量GABA阳性F终末。MTN终末参与不规则形状的终末聚集，其中包含许多F终末和树突状突起，并被神经胶质片包围。视网膜终末聚集成小的圆形排列，与中央树突接触。
