Lee Kun-Ze, Huang Yi-Jia, Tsai I-Lun
Department of Biological Sciences, College of Science, National Sun Yat-sen University, Kaohsiung, Taiwan.
J Appl Physiol (1985). 2014 Feb 15;116(4):395-405. doi: 10.1152/japplphysiol.01001.2013. Epub 2013 Nov 27.
The present study was designed to investigate the impact of midcervical spinal cord injury on respiratory outputs and compare respiratory recovery following high- vs. midcervical spinal injury. A unilateral hemisection (Hx) in the spinal cord at C2 or C4 was performed in adult rats. Respiratory behaviors of unanesthetized animals were measured at normoxic baseline and hypercapnia by whole body plethysmography at 1 day and 1, 2, 4, and 8 wk after spinal injury. C2Hx and C4Hx induced a similar rapid shallow breathing pattern at 1 day postinjury. The respiratory frequency of C4Hx animals gradually returned to normal, but the tidal volume from 1 to 8 wk postinjury remained lower than that of the control animals. Linear regression analyses indicated that the tidal volume recovery was greater in the C4Hx animals than in the C2Hx animals at the baseline, but not at hypercapnia. The bilateral phrenic nerve activity was recorded in anesthetized animals under different respiratory drives at 8-9 wk postinjury. The phrenic burst amplitude ipsilateral to the lesion reduced following both high- and midcervical Hx; however, the ability to increase activity was lower in the C4Hx animals than in the C2Hx animals. When the data were normalized by the maximal inspiratory effort during asphyxia, the phrenic burst amplitude enhanced in the C4Hx animals, but reduced in the C2Hx animals compared with the control animals. These results suggest that respiratory deficits are evident following midcervical Hx, and that respiratory recovery and neuroplasticity of phrenic outputs are different following high- vs. midcervical spinal injury.
本研究旨在调查颈髓中部损伤对呼吸输出的影响，并比较高位与颈髓中部损伤后的呼吸恢复情况。在成年大鼠的脊髓C2或C4处进行单侧半横断（Hx）。在脊髓损伤后1天以及1、2、4和8周，通过全身体积描记法在常氧基线和高碳酸血症状态下测量未麻醉动物的呼吸行为。C2Hx和C4Hx在损伤后1天均诱导出相似的快速浅呼吸模式。C4Hx动物的呼吸频率逐渐恢复正常，但损伤后1至8周的潮气量仍低于对照动物。线性回归分析表明，在基线时，C4Hx动物的潮气量恢复程度大于C2Hx动物，但在高碳酸血症状态下并非如此。在损伤后8 - 9周，在麻醉动物处于不同呼吸驱动状态下记录双侧膈神经活动。高位和颈髓中部Hx后，损伤同侧的膈神经爆发幅度均降低；然而，C4Hx动物增加活动的能力低于C2Hx动物。当数据通过窒息期间的最大吸气努力进行标准化时，与对照动物相比，C4Hx动物的膈神经爆发幅度增强，而C2Hx动物的膈神经爆发幅度降低。这些结果表明，颈髓中部Hx后呼吸功能缺陷明显，并且高位与颈髓中部脊髓损伤后的呼吸恢复和膈神经输出的神经可塑性有所不同。
