Chmielowska J, Pons T P
Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, MD 20892, USA.
J Comp Neurol. 1995 Sep 25;360(3):377-92. doi: 10.1002/cne.903600302.
We examined the pattern of cytochrome oxidase (CO), Nissl staining, and gamma-amino butyric acid (GABA) immunoreactivity in the ventroposterior lateral nucleus (VPL) of the thalamus in monkeys that received no, total, or subtotal, ablation of the hand representations in postcentral somatosensory cortex. In unoperated animals, the region of VPL representing the hand was characterized by relatively dense and homogeneous CO staining throughout the rostral-caudal extent of VPL. Counts of neurons in the VPL hand representation from adjacent thalamic sections processed for Nissl and GABA immunostaining indicated that there were approximately 261.4 neurons/mm2 of which 78.4/mm2 stained positive for GABA. GABA(+) puncta-like terminals were readily apparent throughout the VPL. By contrast, animals that received total removals of the postcentral hand representations showed a dramatic reduction in CO staining in the VPL, which was confined to the expected location of the thalamic hand representation. Counts of neurons in the affected region from adjacent sections that underwent Nissl staining and GABA immunostaining also revealed a dramatic reduction of Nissl-stained neurons, with a smaller reduction in the number of neurons staining positive for GABA. Specifically, large to medium-sized (> 180 microns 2) GABA(-) neurons were virtually eliminated in the affected portion of the VPL, and the numbers of GABA(+) neurons were significantly reduced. The remaining population of GABA(+) neurons was typically shrunken, and no GABA(+) puncta-like terminals were observed in the affected region. The results obtained after subtotal ablation of the postcentral hand representations (only one postcentral area spared, 3b or 3a) differed from those obtained when total removals were made. Instead of virtually complete degeneration of medium-sized to large neurons throughout the hand representation in VPL, as was the case with total removals, after partial removals, we found alternating regions in the VPL hand representation that appeared qualitatively normal, or dramatically degenerated. Thalamic sections stained with CO revealed light, moderate, and darkly stained patches of label within the hand representation in VP, depending on the type of cortical ablation. The most dramatic reduction of Nissl-stained neurons coincided precisely with the lightest staining CO patches. Interestingly, the only statistically significant reduction in the number of GABA(+) neurons occurred in the light CO patches. In the thalamic regions coincident with the dark and moderately stained CO patches, the number of medium-sized and large neurons decreased, but the number of GABA(+) neurons was comparable to normal. Optical density measurements of the dark patches also indicated a statistically significant difference from normal CO staining in this region.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了在中央后体感皮层手部表征未被损毁、完全损毁或部分损毁的猴子丘脑腹后外侧核（VPL）中细胞色素氧化酶（CO）、尼氏染色以及γ-氨基丁酸（GABA）免疫反应性的模式。在未手术的动物中，VPL中代表手部的区域在VPL的整个前后范围内具有相对密集且均匀的CO染色特征。对用于尼氏染色和GABA免疫染色的相邻丘脑切片中VPL手部表征区域的神经元计数表明，大约有261.4个神经元/mm²，其中78.4个/mm²的神经元GABA染色呈阳性。GABA（+）点状终末在整个VPL中很容易观察到。相比之下，接受中央后手部表征完全切除的动物，VPL中的CO染色显著减少，局限于丘脑手部表征的预期位置。对相邻切片中受影响区域进行尼氏染色和GABA免疫染色后的神经元计数也显示，尼氏染色的神经元显著减少，而GABA染色阳性的神经元数量减少幅度较小。具体而言，VPL受影响部分中大体到中等大小（>180微米²）的GABA（-）神经元几乎消失，GABA（+）神经元数量显著减少。剩余的GABA（+）神经元通常萎缩，在受影响区域未观察到GABA（+）点状终末。中央后手部表征部分切除（仅一个中央后区域保留，3b或3a）后获得的结果与完全切除时不同。与完全切除时VPL中手部表征区域内中等大小到大型神经元几乎完全退化的情况不同，部分切除后，我们在VPL手部表征区域发现了交替出现的区域，这些区域在质量上要么正常，要么显著退化。用CO染色的丘脑切片显示，根据皮层切除的类型，VP手部表征区域内有浅、中、深染色的标记斑块。尼氏染色神经元减少最显著的区域恰好与CO染色最浅的斑块重合。有趣的是，GABA（+）神经元数量唯一具有统计学意义的减少发生在CO染色浅的斑块中。在与CO染色深和中等的斑块重合的丘脑区域，中等大小和大型神经元数量减少，但GABA（+）神经元数量与正常情况相当。对深色斑块的光密度测量也表明该区域与正常CO染色存在统计学上显著的差异。（摘要截短至400字）
