Objective. The purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation. Approach. Adult, male, Sprague Dawley rats were randomly assigned to a Healthy or SCI group. SCI rats were given a 175 kDyn dorsal midline contusion injury at the level of the T8 vertebrae. At 4 weeks post-SCI, intracortical microstimulation (ICMS) was delivered at several sites in the hindlimb motor cortex of anesthetized rats, and evoked neural activity was recorded from corresponding sites throughout the dorsoventral depths of the spinal cord and EMG activity from hindlimb muscles. Main results. In healthy rats, post-ICMS spike histograms showed reliable, evoked spike activity during a short-latency epoch 10–12 ms after the initiation of the ICMS pulse train (short). Longer latency spikes occurred between ∼20 and 60 ms, generally following a Gaussian distribution, rising above baseline at time L _ON, followed by a peak response (L _p), and then falling below baseline at time L _OFF. EMG responses occurred between L _ON and L _p( 25–27 ms). In SCI rats, short-latency responses were still present, long-latency responses were disrupted or eliminated, and EMG responses were never evoked. The retention of the short-latency responses indicates that spared descending spinal fibers, most likely via the cortico-reticulospinal pathway, can still depolarize spinal cord neurons after a dorsal midline contusion injury. Significance. This study provides novel insights into the role of alternate pathways for voluntary control of hindlimb movements after SCI that disrupts the corticospinal tract in the rat.

客观的。本研究的目的是确定脊髓损伤 (SCI) 对皮质电刺激在大鼠后肢脊髓中诱发的尖峰活动的影响。方法。成年雄性 Sprague Dawley 大鼠被随机分配到健康组或 SCI 组。对 SCI 大鼠的 T8 椎骨水平进行 175 kDyn 背侧中线挫伤。SCI后4周，在麻醉大鼠后肢运动皮层的几个部位进行皮质内微刺激（ICMS），记录整个脊髓背腹深度相应部位的诱发神经活动和后肢肌肉的肌电图活动。主要结果。在健康大鼠中，ICMS 后尖峰直方图显示，在 ICMS 脉冲序列（短）启动后 10-12 毫秒的短潜伏期内，可靠的诱发尖峰活动。较长的延迟峰值发生在~20 和 60 ms 之间，通常遵循高斯分布，在时间L _ON上升到基线以上，随后出现峰值响应 ( L _p )，然后在时间L _OFF下降到基线以下。EMG 反应发生在L _ON和L _p（25-27 毫秒）之间。在 SCI 大鼠中，短潜伏期反应仍然存在，长潜伏期反应被破坏或消除，并且从未诱发肌电图反应。短潜伏期反应的保留表明，在背中线挫伤后，幸存的下行脊髓纤维（最有可能通过皮质网状脊髓途径）仍然可以使脊髓神经元去极化。意义。这项研究为大鼠脊髓损伤后皮质脊髓束受损后自主控制后肢运动的替代途径的作用提供了新的见解。