University of Florida, College of Medicine, McKnight Brain Institute, Department of Neuroscience, Gainesville, FL 32611, United States.
Respir Physiol Neurobiol. 2012 Sep 30;183(3):186-92. doi: 10.1016/j.resp.2012.06.006. Epub 2012 Jun 13.
Anatomical and neurophysiological evidence indicates that thoracic interneurons can serve a commissural function and activate contralateral motoneurons. Accordingly, we hypothesized that respiratory-related intercostal (IC) muscle electromyogram (EMG) activity would be only modestly impaired by a unilateral cervical spinal cord injury. Inspiratory tidal volume (VT) was recorded using pneumotachography and EMG activity was recorded bilaterally from the 1st to 2nd intercostal space in anesthetized, spontaneously breathing rats. Studies were conducted at 1-3 days, 2 wks or 8 wks following C2 spinal cord hemisection (C2HS). Data were collected during baseline breathing and a brief respiratory challenge (7% CO(2)). A substantial reduction in inspiratory intercostal EMG bursting ipsilateral to the lesion was observed at 1-3 days post-C2HS. However, a time-dependent return of activity occurred such that by 2 wks post-injury inspiratory intercostal EMG bursts ipsilateral to the lesion were similar to age-matched, uninjured controls. The increases in ipsilateral intercostal EMG activity occurred in parallel with increases in VT following the injury (R=0.55; P<0.001). We conclude that plasticity occurring within a "crossed-intercostal" circuitry enables a robust, spontaneous recovery of ipsilateral intercostal activity following C2HS in rats.
解剖学和神经生理学证据表明，胸内神经元可以发挥联络功能，激活对侧运动神经元。因此，我们假设单侧颈脊髓损伤只会对呼吸相关的肋间（IC）肌肌电图（EMG）活动产生适度的影响。在麻醉、自主呼吸的大鼠中，使用气动流量测定法记录吸气潮气量（VT），并从第 1 到第 2 肋间空间双侧记录 EMG 活动。在 C2 脊髓半切（C2HS）后 1-3 天、2 周或 8 周进行研究。在基线呼吸和短暂的呼吸挑战（7%CO2）期间收集数据。在 C2HS 后 1-3 天，观察到病变同侧吸气肋间 EMG 爆发明显减少。然而，活动出现了时间依赖性的恢复，以至于在损伤后 2 周，病变同侧吸气肋间 EMG 爆发与年龄匹配的未受伤对照组相似。在损伤后，同侧肋间 EMG 活动的增加与 VT 的增加平行（R=0.55；P<0.001）。我们的结论是，在“交叉肋间”回路中发生的可塑性使得大鼠 C2HS 后同侧肋间活动能够实现强大、自发的恢复。
