Akintunde A, Buxton D F
Department of Anatomy and Histology, College of Veterinary Medicine, Auburn University, AL 36849-5518.
Brain Res. 1992 Mar 13;575(1):86-92. doi: 10.1016/0006-8993(92)90427-b.
Cells of origin for corticospinal fibers in the rat were identified following retrograde transport of Fluoro-Gold (FG), Propidium iodide (PI), Fast blue (FB), and Diamidino yellow (DY) injected unilaterally into lumbar (FG), mid-thoracic (PI), cervical enlargement (FB), and cranial cervical (DY) spinal gray matter. Most labeled neurons were contralateral to injection in lamina V and ranged from small to very large. These cells occupied two distinct cortical regions: one rostral and the other larger and more caudal. Neurons of the rostral region projected axons solely to cervical spinal segments whereas neurons of the caudal region projected fibers to all spinal segments. Somatotopically, most neurons projecting to lumbar segments were most medial. More than 98% of all labeled cortical neurons contained only a single fluorescent tracer; however, within a single tissue section each of the 4 tracers could be found in these single labeled neurons. The few double labeled neurons contained only cervical (DY + FB) or thoracolumbar (PI + FG) tracers. No triple or quadruple labeled cells were seen. Hence morphological evidence is presented that corticospinal axons branch to terminate in more than one spinal region, but these collateral terminations are restricted to only a few adjacent spinal segments.
通过将荧光金（FG）、碘化丙啶（PI）、快蓝（FB）和双脒基黄（DY）单侧注入大鼠腰段（FG）、胸中段（PI）、颈膨大（FB）和颈颅段（DY）脊髓灰质后进行逆行运输，确定了大鼠皮质脊髓纤维的起源细胞。大多数标记神经元位于注射部位对侧的V层，大小从小到非常大不等。这些细胞占据两个不同的皮质区域：一个位于吻侧，另一个更大且位于尾侧。吻侧区域的神经元仅将轴突投射到颈段脊髓节段，而尾侧区域的神经元将纤维投射到所有脊髓节段。在躯体定位上，投射到腰段节段的大多数神经元位于最内侧。所有标记的皮质神经元中超过98%仅含有一种荧光示踪剂；然而，在单个组织切片中，这4种示踪剂中的每一种都可以在这些单标记神经元中找到。少数双标记神经元仅含有颈段（DY + FB）或胸腰段（PI + FG）示踪剂。未观察到三重或四重标记细胞。因此，提供了形态学证据表明皮质脊髓轴突分支并终止于不止一个脊髓区域，但这些侧支终末仅限于少数相邻的脊髓节段。
