Kanagal Srikanth G, Muir Gillian D
Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan Saskatoon, Canada SK S7N 5B4.
Exp Neurol. 2007 Jun;205(2):513-24. doi: 10.1016/j.expneurol.2007.03.014. Epub 2007 Mar 23.
Spinal cord injury models often involve damage to the corticospinal tract (CST) because of the functional importance of this pathway in humans. In rats, the main component of the CST travels in the dorsal funiculus and cannot be damaged without concurrent damage to overlying sensory fibers. To distinguish deficits due to the loss of CST from those due to sensory fiber damage, we bilaterally axotomized ascending sensory fibers in dorsal columns without CST damage in one group of rats (ascending sensory pathways, ASP) and compared the results to a group with damage to ascending sensory fibers with CST damage (ASP+CST). We assessed the ability of rats to perform a skilled reaching task and to walk over a horizontal ladder. We also measured the forces exerted on the ground (ground reaction forces, GRF) and limb contact patterns produced during overground locomotion. After ASP lesions alone, endpoint measurements of reaching success and footslip errors on the ladder showed transitory impairments, although detailed analysis revealed persistent deficits in skilled forelimb movements. ASP+CST lesions caused persistent deficits in reaching success and ladder footslips throughout the 8-week post-surgical period. Measurement of GRFs and limb timing during overground locomotion revealed differences in both groups at 8 weeks post-surgery compared to pre-surgical values, but no differences between ASP and ASP+CST groups. These results emphasize the normal contribution of both ascending sensory axons and CST axons during skilled limb movements and support a role for ascending sensory information, but not descending CST input, during overground locomotion. These results also illustrate the value of using sensitive methods to reveal detailed behavioural changes after spinal injury.
由于皮质脊髓束（CST）在人类中的功能重要性，脊髓损伤模型通常涉及该通路的损伤。在大鼠中，CST的主要成分走行于背侧索，若不同时损伤其上方的感觉纤维则无法损伤CST。为了区分因CST丧失所致的功能缺陷与因感觉纤维损伤所致的功能缺陷，我们在一组大鼠中双侧切断背柱中的上行感觉纤维而不损伤CST（上行感觉通路，ASP），并将结果与另一组上行感觉纤维与CST均损伤的大鼠（ASP+CST）进行比较。我们评估了大鼠执行熟练抓握任务以及在水平梯子上行走的能力。我们还测量了在地面行走时施加在地面上的力（地面反作用力，GRF）以及肢体接触模式。单独进行ASP损伤后，抓握成功率和梯子上失足错误的终点测量显示有短暂损伤，尽管详细分析揭示了熟练前肢运动存在持续缺陷。在术后8周的整个时间段内，ASP+CST损伤导致抓握成功率和梯子失足方面持续存在缺陷。对地面行走期间GRF和肢体时间的测量显示，与术前值相比，两组在术后8周均存在差异，但ASP组和ASP+CST组之间无差异。这些结果强调了上行感觉轴突和CST轴突在熟练肢体运动过程中的正常作用，并支持上行感觉信息在地面行走过程中的作用，但不支持下行CST输入的作用。这些结果还说明了使用敏感方法揭示脊髓损伤后详细行为变化的价值。
