Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke, National Institutes of Health , Bethesda, MD, USA.
Front Neurosci. 2014 May 30;8:124. doi: 10.3389/fnins.2014.00124. eCollection 2014.
The interplay of the neuronal discharge patterns regarding respiration and locomotion was investigated using electrophysiological techniques in a decerebrate and arterially perfused in situ mouse preparation. The phrenic, tibial, and/or peroneal nerve discharge became clearly organized into discharge episodes of increasing frequency and duration, punctuated by periods of quiescence as the perfusion flow rate increased at room temperature. The modulated sympathetic tone induced by the hyperoxic/normocapnic state was found to activate the locomotor pattern generator (LPG) via descending pathways and generate a left and right alternating discharge during discharge episodes in the motor nerves. The rhythm coupling of respiration and locomotion occurred at a 1:1 frequency ratio. Although the phrenic discharge synchronized with the tibial discharge at all flow rates tested, the time lag between peaks of the two discharges during locomotion was ≈400 ms rather than ≈200 ms, suggesting spinal feedback via ascending pathways. The incidence of the phrenic and tibial discharge episodes decreased by ≈50% after spinalization at the twelfth thoracic cord and the respiratory rhythm was more regular. These results indicate that: (i) locomotion can be generated in a hyperoxic/normocapnic state induced by specific respiratory conditions, (ii) the central mechanism regarding entrainment of respiratory and locomotor rhythms relies on spinal feedback via ascending pathways, initiated by the activated LPG generating locomotion, and (iii) the increase in respiratory rate seen during locomotion is caused not only by afferent mechanical and nociceptive inputs but also by impulses from the activated spinal cord producing a locomotor-like discharge via ascending pathways.
在去大脑和动脉灌注的原位小鼠模型中，使用电生理技术研究了与呼吸和运动相关的神经元放电模式的相互作用。膈神经、胫神经和/或腓神经的放电明显变得更加有规律，频率和持续时间增加，随着灌注流量在室温下增加，静息期也随之增加。发现由高氧/正常碳酸血症诱导的调制交感神经张力通过下行途径激活运动模式发生器（LPG），并在运动神经的放电过程中产生左右交替放电。呼吸和运动的节律耦合发生在 1:1 的频率比。尽管在所有测试的流速下，膈神经放电都与胫神经放电同步，但在运动过程中两个放电峰之间的时间滞后约为 400ms，而不是约 200ms，这表明通过上行途径存在脊髓反馈。在第十二胸椎处进行脊髓切断后，膈神经和胫神经放电的发生率下降了约 50%，呼吸节律变得更加规则。这些结果表明：（i）在特定呼吸条件下的高氧/正常碳酸血症状态下可以产生运动；（ii）呼吸和运动节律的同步化的中枢机制依赖于通过上行途径的脊髓反馈，由激活的产生运动的 LPG 引发；（iii）运动时呼吸频率的增加不仅是由传入的机械和伤害性输入引起的，还可能是由激活的脊髓产生的类似于运动的放电通过上行途径引起的。
