Lavrov Igor, Gerasimenko Yury P, Ichiyama Ronaldo M, Courtine Gregoire, Zhong Hui, Roy Roland R, Edgerton V Reggie
Department of Physiological Science, University of California, Los Angeles, CA 90095-1527, USA.
J Neurophysiol. 2006 Oct;96(4):1699-710. doi: 10.1152/jn.00325.2006. Epub 2006 Jul 5.
Changes in epidurally induced (S1) spinal cord reflexes were studied as a function of the level of restoration of stepping ability after spinal cord transection (ST). Three types of responses were observed. The early response (ER) had a latency of 2.5 to 3 ms and resulted from direct stimulation of motor fibers or motoneurons. The middle response (MR) had a latency of 5 to 7 ms and was monosynaptic. The late response (LR) had a latency of 9 to 11 ms and was polysynaptic. After a complete midthoracic ST, the LR was abolished, whereas the MR was facilitated and progressively increased. The LR reappeared about 3 wk after ST and increased during the following weeks. Restoration of stepping induced by epidural stimulation at 40 Hz coincided with changes in the LR. During the first 2 wk post-ST, rats were unable to step and electrophysiological assessment failed to show any LR. Three weeks post-ST, epidural stimulation resulted in a few steps and these coincided with reappearance of the LR. The ability of rats to step progressively improved from wk 3 to wk 6 post-ST. There was a continuously improved modulation of rhythmic EMG bursts that was correlated with restoration of the LR. These results suggest that restoration of polysynaptic spinal cord reflexes after complete ST coincides with restoration of stepping function when facilitated by epidural stimulation. Combined, these findings support the view that restoration of polysynaptic spinal cord reflexes induced epidurally may provide a measure of functional restoration of spinal cord locomotor networks after ST.
研究了硬膜外诱导的（S1）脊髓反射变化与脊髓横断（ST）后步行能力恢复水平之间的关系。观察到三种类型的反应。早期反应（ER）潜伏期为2.5至3毫秒，由运动纤维或运动神经元的直接刺激引起。中期反应（MR）潜伏期为5至7毫秒，为单突触反应。晚期反应（LR）潜伏期为9至11毫秒，为多突触反应。在完全胸段脊髓横断后，LR消失，而MR增强并逐渐增加。LR在脊髓横断后约3周重新出现，并在接下来的几周内增加。40赫兹硬膜外刺激诱导的步行恢复与LR的变化一致。在脊髓横断后的前2周，大鼠无法行走，电生理评估未显示任何LR。脊髓横断后3周，硬膜外刺激导致一些步行动作，这些动作与LR的重新出现一致。大鼠的步行能力从脊髓横断后第3周逐渐改善到第6周。有节律的肌电图爆发的调制不断改善，这与LR的恢复相关。这些结果表明，完全脊髓横断后多突触脊髓反射的恢复与硬膜外刺激促进的步行功能恢复一致。综合这些发现支持这样一种观点，即硬膜外诱导的多突触脊髓反射的恢复可能为脊髓横断后脊髓运动网络的功能恢复提供一种衡量标准。
