Harnie Jonathan, Côté-Sarrazin Célia, Hurteau Marie-France, Desrochers Etienne, Doelman Adam, Amhis Nawal, Frigon Alain
Faculty of Medicine and Health Sciences, Department of Pharmacology-Physiology, Université de Sherbrooke , Sherbrooke, Quebec , Canada.
J Neurophysiol. 2018 Sep 1;120(3):1274-1285. doi: 10.1152/jn.00812.2017. Epub 2018 Jun 13.
Speed modulation requires spatiotemporal adjustments and altered neural drive to different muscles. The loss of certain muscles produces changes in the locomotor pattern and functional compensation. However, how the loss of specific muscles affects speed modulation has not been specifically investigated. Here, we denervated the lateral gastrocnemius and soleus muscles unilaterally in seven cats that had recovered hindlimb locomotion following complete spinal transection (spinal cats). Hindlimb locomotion was tested at 10 speeds, from 0.1 to 1.0 m/s, before, 1-2 days, and 1-8 wk after denervation. Six of seven cats performed hindlimb locomotion 1-2 days postdenervation at all speeds, with the exception of two out of those six cats that did not perform stable stepping at 0.9 and 1.0 m/s. All seven cats performed hindlimb locomotion 1-8 wk postdenervation at all speeds. In some cats, at 1-2 days postdenervation, the ipsilateral hindlimb performed more steps than the contralateral hindlimb, particularly at slow speeds. This 2:1 coordination disappeared over time. In three cats, the linear increase in the amplitude of the electromyography of the ipsilateral medial gastrocnemius was reduced with increasing speed early after denervation before recovering later on. Overall, the results indicate that spinal circuits interacting with sensory feedback from the hindlimbs compensate for the partial loss of ankle extensors, retaining the ability to modulate locomotor speed. NEW & NOTEWORTHY We investigated speed modulation after denervating 2 ankle extensors unilaterally at 10 treadmill speeds in spinal-transected cats. Although we observed new forms of left-right coordination and changes in muscle activity of a remaining synergist, modulation of spatiotemporal variables with increasing speed was largely maintained after denervation. The results indicate that spinal locomotor centers interacting with sensory feedback compensate for the loss of ankle extensors, allowing speed modulation.
速度调节需要时空调整以及对不同肌肉的神经驱动改变。特定肌肉的丧失会导致运动模式的变化和功能补偿。然而，特定肌肉的丧失如何影响速度调节尚未得到专门研究。在此，我们对七只在完全脊髓横断后恢复后肢运动的猫（脊髓猫）单侧去神经支配腓肠肌外侧头和比目鱼肌。在去神经支配前、去神经支配后1 - 2天以及1 - 8周，以0.1至1.0米/秒的10种速度测试后肢运动。七只猫中有六只在去神经支配后1 - 2天能以所有速度进行后肢运动，但这六只猫中有两只在0.9和1.0米/秒时不能进行稳定的迈步。所有七只猫在去神经支配后1 - 8周能以所有速度进行后肢运动。在一些猫中，去神经支配后1 - 2天，同侧后肢比 contralateral 后肢迈出更多步，尤其是在低速时。这种2:1的协调随着时间消失。在三只猫中，去神经支配后早期，同侧腓肠肌内侧头肌电图幅度随速度增加的线性增加减少，随后恢复。总体而言，结果表明与后肢感觉反馈相互作用的脊髓回路可补偿踝伸肌的部分丧失，保留调节运动速度的能力。新发现与值得注意之处我们在脊髓横断的猫中以10种跑步机速度单侧去神经支配2块踝伸肌后研究速度调节。尽管我们观察到了新的左右协调形式以及剩余协同肌肌肉活动的变化，但去神经支配后随着速度增加对时空变量的调节在很大程度上得以维持。结果表明与感觉反馈相互作用的脊髓运动中枢可补偿踝伸肌的丧失，实现速度调节。
