Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.
J Comp Neurol. 2010 Jul 15;518(14):2645-65. doi: 10.1002/cne.22391.
Large, mediolaterally oriented neurons in lamina I of the spinal cord, frequently referred to as marginal cells of Waldeyer, are known to project to supraspinal targets via the anterolateral tract (ALT). Although dendritic organization of lamina I neurons has been extensively studied, little is known about their local axonal morphology and branching. With the help of oblique illumination, we visually identified large lamina I neurons in the isolated lumbar enlargement (L1-L6) of the spinal cord of P14-P20 rats. By using intracellular and cell-attached biocytin injections, we achieved extensive axonal and dendritic labeling in 77 lamina I cells, 40 of which were identified as ALT projection neurons. In the majority of the cases (n = 28), the main axon of these projection neurons gave rise to one or more thin collaterals on the ipsilateral side. Based on their trajectory and location, these collaterals could be divided into three major categories: dorsal, lateral, and ventral. Lamina I projection neurons had dorsal (n = 5), lateral (n = 8), or ventral (n = 6) collaterals only or a combination of these collateral types (n = 9). Our results suggest that lamina I ALT projection neurons can additionally function as local-circuit and propriospinal neurons participating in intra- and intersegmental spinal cord processing.
脊髓 I 层中大型、偏侧定向的神经元，通常被称为 Waldeyer 的边缘细胞，已知通过前外侧束 (ALT) 投射到脊髓上靶位。虽然 I 层神经元的树突组织已被广泛研究，但对其局部轴突形态和分支知之甚少。借助斜向照明，我们在 P14-P20 大鼠的孤立腰椎膨大部 (L1-L6) 的脊髓中可视地识别出大型 I 层神经元。通过使用细胞内和细胞附着生物素注射，我们在 77 个 I 层细胞中实现了广泛的轴突和树突标记，其中 40 个被鉴定为 ALT 投射神经元。在大多数情况下（n = 28），这些投射神经元的主轴突在同侧产生一个或多个细侧支。根据它们的轨迹和位置，这些侧支可分为三大类：背侧、外侧和腹侧。I 层投射神经元只有背侧（n = 5）、外侧（n = 8）或腹侧（n = 6）侧支，或者具有这些侧支类型的组合（n = 9）。我们的结果表明，I 层 ALT 投射神经元还可以作为局部回路和 propriospinal 神经元发挥作用，参与脊髓内和脊髓间的处理。
