McAllister J P, Wells J
J Comp Neurol. 1981 Apr 1;197(2):271-301. doi: 10.1002/cne.901970208.
The structural plan of the ventral posterolateral nucleus (VLP) in the rat was analyzed by using a variety of techniques to study the pattern of distribution of the ascending afferent fibers and the synaptology of the neuropil within this somatosensory relay nucleus. Golgi stains, Fink-Heimer methods, HRP labeling methods, and electron microscopy were all used in the analysis. The neurons in VPL are aligned in rostrocaudal and dorsoventral rows that are roughly parallel to the curvature of the external medullary lamina (EML) and curve partially around the rostral pole of the ventral posteromedial nucleus (VPM). Golgi-impregnated sections reveal that the dendritic trees of the VPL neurons conform in general to the laminar pattern of VPL. Thick proximal dendrites extend about 25 mu m from the cell bodies. Most proximal dendrites are aligned with the laminae of VPL but the distal dendrites spread over many laminae within VPL. The inputs from the dorsal column nuclei (DCN) end only on proximal dendrites as large, round-vesicle terminals. About 20--25% of the small round-vesicle terminals originate in the cerebral cortex and synapse only on the distal dendrites. The third type of synapse contains many flattened vesicles and is of unknown origin. No serial synapses or vesicle-containing dendrites were observed. Input from the spinal cord projects to two segregated zones which are transitional between the ventral lateral nucleus (VL) and VPL rostrally and between the posterior thalamic complex (PO) and VPL caudally. Each transition zone contains neurons characteristic of both VPL and the adjacent region. Ascending afferent projections were demonstrated by the antegrade transport of HRP following injections into the ventral mesencephalon and by Fink-Heimer stains of degeneration resulting from small lesions of the DCN. Both methods indicate that large-caliber axons course parallel to each other and give off collaterals that diverge to widespread areas of the VPL. The widespread terminal fields that result do not conform to the laminar pattern of the nucleus. Small punctate lesions of DCN result in sparse degeneration that is also widespread in VPL. Structures which appear to be clusters of terminal arborizations of the ascending afferent input were also observed in VPL. These results suggest that somatotopy and modality separation in VPL may be determined either by intrinsic and/or corticothalamic morphological relationships and not by precise topographical ordering of sensory input.
采用多种技术分析大鼠腹后外侧核（VLP）的结构，以研究该体感中继核内传入纤维的分布模式及神经毡的突触学。分析过程中使用了高尔基染色法、芬克 - 海默法、辣根过氧化物酶（HRP）标记法及电子显微镜技术。VPL中的神经元排列成大致平行于外髓板（EML）弯曲的前后和背腹方向的行，并部分围绕腹后内侧核（VPM）的嘴侧极弯曲。高尔基浸染切片显示，VPL神经元的树突一般符合VPL的分层模式。粗大的近端树突从细胞体延伸约25μm。大多数近端树突与VPL的层对齐，但远端树突分布在VPL的许多层上。来自背柱核（DCN）的输入仅以大的圆形囊泡终末终止于近端树突上。约20% - 25%的小圆形囊泡终末起源于大脑皮质，仅与远端树突形成突触。第三种突触含有许多扁平囊泡，来源不明。未观察到连续突触或含囊泡的树突。来自脊髓的输入投射到两个分离的区域，这两个区域在前部位于腹外侧核（VL）和VPL之间过渡，在后部位于丘脑后复合体（PO）和VPL之间过渡。每个过渡区都包含VPL和相邻区域特有的神经元。通过将HRP注入腹侧中脑后的顺行运输以及DCN小损伤导致的退变的芬克 - 海默染色法，证实了上行传入投射。两种方法均表明，大口径轴突彼此平行走行，并发出分支扩散到VPL的广泛区域。由此产生的广泛终末场不符合该核的分层模式。DCN的小点状损伤导致稀疏的退变，在VPL中也很广泛。在VPL中还观察到似乎是上行传入输入终末分支簇的结构。这些结果表明，VPL中的躯体定位和模式分离可能由内在和/或皮质 - 丘脑形态学关系决定，而非由感觉输入的精确拓扑排序决定。
