van Groen T, Wyss J M
Department of Cell Biology, University of Alabama, Birmingham 35294.
J Comp Neurol. 1992 Oct 15;324(3):427-48. doi: 10.1002/cne.903240310.
The laterodorsal nucleus (LD) of the thalamus is an important source of thalamic afferents to the limbic cortex, but the topography and lamination of these projections has not been investigated in detail. Using the anterograde transport of Phaseolus vulgaris leucoagglutinin and Fluoro-Ruby, the present study demonstrates that in the rat, LD projects to infraradiata, precentral agranular, retrosplenial, visual (area 18b), subicular, and entorhinal cortices. Each subregion of LD has a distinct pattern of terminals within these cortical areas. The rostral part and the dorsalmost part of LD project densely to retrosplenial granular a (Rga) cortex, presubiculum and parasubiculum. Slightly more caudal parts of dorsal LD project primarily to the postsubiculum. More ventral parts of LD project primarily to retrosplenial dysgranular (Rdg) and retrosplenial granular b (Rgb) cortices. The projection of LD to area 18b originates from cells in the caudalmost part of LD. In each cortical region, LD terminals display distinct laminar patterns. In area 18b and the adjacent Rdg cortex, the LD terminal field is in layers I, III, and IV, but in both the Rgb and Rga cortices the terminal field is located predominantly in layer I. In the postsubiculum the LD terminals are distributed to layers I and III/IV and extend into superficial layer V; in the presubiculum and the parasubiculum the LD terminals are only in the deep layers (i.e., layers IV-VI). A small number of LD axons terminate in the deep layers (i.e., layers IV-VI) of the medial entorhinal cortex. These results indicate that each area of LD has a distinct projection to limbic and adjacent neocortex.
丘脑的外侧背核（LD）是丘脑向边缘皮质传入纤维的重要来源，但这些投射的拓扑结构和分层尚未得到详细研究。本研究利用菜豆白细胞凝集素和荧光红宝石的顺行运输，证明在大鼠中，LD投射到辐射下皮质、中央前颗粒皮质、脾后皮质、视觉皮质（18b区）、海马下托和内嗅皮质。LD的每个亚区在这些皮质区域内都有独特的终末模式。LD的嘴侧部分和最背侧部分密集投射到脾后颗粒a（Rga）皮质、前下托和旁下托。背侧LD稍靠尾侧的部分主要投射到后下托。LD更靠腹侧的部分主要投射到脾后颗粒减少皮质（Rdg）和脾后颗粒b（Rgb）皮质。LD向18b区的投射起源于LD最尾侧部分的细胞。在每个皮质区域，LD终末呈现出不同的分层模式。在18b区和相邻的Rdg皮质中，LD终末场位于I、III和IV层，但在Rgb和Rga皮质中，终末场主要位于I层。在后下托中，LD终末分布于I层和III/IV层，并延伸至V层浅层；在前下托和旁下托中，LD终末仅位于深层（即IV - VI层）。少数LD轴突终止于内嗅皮质内侧的深层（即IV - VI层）。这些结果表明，LD的每个区域对边缘皮质和相邻新皮质都有独特的投射。
