Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan.
Graduate School of Health Science, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-Gun, Ibaraki, 300-0394, Japan.
Sci Rep. 2023 Aug 25;13(1):13905. doi: 10.1038/s41598-023-40505-x.
After an individual experiences a cervical cord injury, the cell body's adaptation to the smaller size of phrenic motoneurons occurs within several weeks. It is not known whether a routine hypercapnic load can alter this adaptation of phrenic motoneurons. We investigated this question by using rats with high cervical cord hemisection. The rats were divided into four groups: control, hypercapnia, sham, and sham hypercapnia. Within 72 h post-hemisection, the hypercapnia groups began a hypercapnic challenge (20 min/day, 4 times/week for 3 weeks) with 7% CO under awake conditions. After the 3-week challenge, the phrenic motoneurons in all of the rats were retrogradely labeled with horseradish peroxidase, and the motoneuron sizes in each group were compared. The average diameter, cross-sectional area, and somal surface area of stained phrenic motoneurons as analyzed by software were significantly smaller in only the control group compared to the other groups. The histogram distribution was unimodal, with larger between-group size differences for motoneurons in the horizontal plane than in the transverse plane. Our findings indicate that a routine hypercapnic challenge may increase the input to phrenic motoneurons and alter the propensity for motoneuron adaptations.
个体经历颈髓损伤后，膈神经运动神经元的胞体在数周内适应较小的体积。目前尚不清楚常规高碳酸血症负荷是否会改变膈神经运动神经元的这种适应性。我们使用高位颈髓半切大鼠来研究这个问题。大鼠分为四组：对照组、高碳酸血症组、假手术组和假手术高碳酸血症组。在半切后 72 小时内，高碳酸血症组开始在清醒状态下接受 7% CO2 的高碳酸血症挑战（20 分钟/天，每周 4 次，持续 3 周）。在 3 周的挑战后，所有大鼠的膈神经运动神经元均用辣根过氧化物酶逆行标记，并比较每组的运动神经元大小。仅在对照组中，软件分析的染色膈神经运动神经元的平均直径、横截面积和体表面积明显小于其他组。直方图分布呈单峰型，在水平平面上的运动神经元的组间大小差异大于在横平面上的运动神经元。我们的发现表明，常规高碳酸血症挑战可能会增加膈神经运动神经元的输入，并改变运动神经元适应性的倾向。
