Datskovskaia A, Carden W B, Bickford M E
Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, Kentucky 40292, USA.
J Comp Neurol. 2001 Jan 29;430(1):85-100. doi: 10.1002/1096-9861(20010129)430:1<85::aid-cne1016>3.0.co;2-k.
One of the largest influences on dorsal lateral geniculate nucleus (dLGN) activity comes from interneurons, which use the neurotransmitter gamma-aminobutyric acid (GABA). It is well established that X retinogeniculate terminals contact interneurons and thalamocortical cells in complex synaptic arrangements known as glomeruli. However, there is little anatomical evidence for the involvement of dLGN interneurons in the Y pathway. To determine whether Y retinogeniculate axons contact interneurons, we injected the superior colliculus (SC) with biotinylated dextran amine (BDA) to backfill retinal axons, which also project to the SC. Within the A lamina of the dLGN, this BDA labeling allowed us to distinguish Y retinogeniculate axons from X retinogeniculate axons, which do not project to the SC. In BDA-labeled tissue prepared for electron microscopic analysis, we subsequently used postembedding immunocytochemical staining for GABA to distinguish interneurons from thalamocortical cells. We found that the majority of profiles postsynaptic to Y retinal axons were GABA-negative dendrites of thalamocortical cells (117/200 or 58.5%). The remainder (83/200 or 41.5%) were GABA-positive dendrites, many of which contained vesicles (59/200 or 29.5%). Thus, Y retinogeniculate axons do contact interneurons. However, these contacts differed from X retinogeniculate axons, in that triadic arrangements were rare. This indicates that the X and Y pathways participate in unique circuitries but that interneurons are involved in the modulation of both pathways.
对背外侧膝状核（dLGN）活动影响最大的因素之一来自中间神经元，它们使用神经递质γ-氨基丁酸（GABA）。众所周知，X视网膜膝状体终末以一种称为小球的复杂突触排列方式与中间神经元和丘脑皮质细胞接触。然而，几乎没有解剖学证据表明dLGN中间神经元参与Y通路。为了确定Y视网膜膝状体轴突是否与中间神经元接触，我们向丘脑上核（SC）注射生物素化葡聚糖胺（BDA）以逆向标记也投射到SC的视网膜轴突。在dLGN的A层内，这种BDA标记使我们能够区分Y视网膜膝状体轴突和不投射到SC的X视网膜膝状体轴突。在为电子显微镜分析准备的BDA标记组织中，我们随后使用GABA的包埋后免疫细胞化学染色来区分中间神经元和丘脑皮质细胞。我们发现，Y视网膜轴突突触后的大多数形态是丘脑皮质细胞的GABA阴性树突（117/200或58.5%）。其余（83/200或41.5%）是GABA阳性树突，其中许多含有囊泡（59/200或29.5%）。因此，Y视网膜膝状体轴突确实与中间神经元接触。然而，这些接触与X视网膜膝状体轴突不同，因为三联体排列很少见。这表明X和Y通路参与独特的神经回路，但中间神经元参与两条通路的调节。
