Khurram Obaid U, Kantor-Gerber Maximilian J, Mantilla Carlos B, Sieck Gary C
Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States.
Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States.
J Neurophysiol. 2025 Aug 1;134(2):698-714. doi: 10.1152/jn.00279.2025. Epub 2025 Jul 28.
Neural drive to the diaphragm muscle (DIAm) for breathing is generated in the medulla and descends primarily ipsilaterally to phrenic motor neurons (PhMNs) in the cervical spinal cord. Neuromotor control of the DIAm during breathing involves motor unit (MU) recruitment, sustained activity, and derecruitment, which may be differentially altered on ipsilateral and contralateral sides after C spinal hemisection (CSH). In awake rats, bilateral DIAm electromyographic (EMG) activity was recorded via chronically implanted electrodes during eupnea in nine Sprague-Dawley rats before and 14 days () after CSH. The durations of MU recruitment and derecruitment were estimated by evaluating EMG signal stationarity, i.e., changes in the mean square average of onset- and offset-aligned 10-ms bins within a longer (e.g., 80 ms) sampling period reflect changes in EMG due to MU recruitment. The amplitudes of DIAm EMG at the end of the recruitment and beginning of the derecruitment phase were measured. On the ipsilateral side, CSH decreased DIAm EMG recruitment amplitude by ∼30% and peak amplitude by ∼35% by , likely reflecting a decrease in the number of MUs recruited. On the contralateral side, CSH increased recruitment amplitude by ∼70% and peak amplitude by ∼80% by , likely reflecting an increase in the number of MUs recruited. The derecruitment amplitude decreased ipsilaterally and increased contralaterally, consistent with the recruitment of higher threshold MUs contralaterally. The present study reveals that the impact of CSH on ipsilateral and contralateral DIAm neuromotor control varies depending on the loss of ipsilateral neural drive. Neuromotor control of the diaphragm muscle (DIAm) after C spinal hemisection (CSH) is impacted differentially between ipsilateral and contralateral sides. We show neural drive to ipsilateral phrenic motor neurons decreases after CSH, leading to a reduction in the number of DIAm motor units (MUs) recruited. Contralateral neural drive increases after CSH, leading to an increase in the number of MU recruited. These results provide novel information about the impact of CSH on DIAm neuromotor control.
呼吸时膈肌的神经驱动在延髓产生，主要沿同侧下行至颈脊髓的膈运动神经元（PhMNs）。呼吸过程中膈肌的神经运动控制涉及运动单位（MU）的募集、持续活动和解募，在颈髓半横断（CSH）后，同侧和对侧的这些过程可能会有不同程度的改变。在清醒大鼠中，通过长期植入的电极在9只Sprague-Dawley大鼠CSH前及术后14天的平静呼吸期间记录双侧膈肌肌电图（EMG）活动。通过评估EMG信号的平稳性来估计MU募集和解募的持续时间，即在较长（如80 ms）采样期内起始和终止对齐的10 ms时间段内均方平均值的变化反映了由于MU募集引起的EMG变化。测量募集末期和解募期开始时膈肌EMG的幅度。在同侧，CSH使膈肌EMG募集幅度在术后14天降低约30%，峰值幅度降低约35%，这可能反映了募集的MU数量减少。在对侧，CSH使募集幅度在术后14天增加约70%，峰值幅度增加约80%，这可能反映了募集的MU数量增加。解募幅度在同侧降低，在对侧增加，这与对侧募集更高阈值的MU一致。本研究表明，CSH对同侧和对侧膈肌神经运动控制的影响因同侧神经驱动的丧失而有所不同。颈髓半横断（CSH）后，同侧和对侧膈肌的神经运动控制受到不同程度的影响。我们发现CSH后同侧膈运动神经元的神经驱动减少，导致募集的膈肌运动单位（MU）数量减少。CSH后对侧神经驱动增加，导致募集的MU数量增加。这些结果提供了关于CSH对膈肌神经运动控制影响的新信息。
