Plastic changes of the neural expression of c-Fos protein in the medullary respiratoryneurons following respiratory muscle training with CO2 breathing in the Wistar rats

呼吸肌训练(RMT)可以改善慢性呼吸系统疾病患者的呼吸肌无力。然而，目前还不清楚RMT是否会诱导呼吸中枢和呼吸肌的适应。我们假设延髓中的呼吸中枢也会适应RMT，在高二氧化碳刺激下，较少的神经元变得招募来实现相同的分钟换气。为了阐明这一假说，比较了短期高二氧化碳刺激(7%CO_2，50%O_2，N_2平衡，90分钟)后RMT大鼠与非训练对照组大鼠延髓c-Fos阳性神经元的数量。对于呼吸肌训练计划，我们使用了高二氧化碳刺激，包括将每只大鼠放在高二氧化碳舱中，以增加每分钟的通气量。RMT大鼠(n=2)被放置在充满7%CO2和50%O2的小室中30min，每周5次，持续4周，而对照组(n=2)被放置在同样充满室内空气的小室中。4周实验结束1.5h后，取延髓轴位切片进行c-Fos免疫组织化学染色，发现RMT组大鼠延髓腹侧和背侧的c-Fos阳性神经元数明显少于对照组。

Respiratory muscle training (RMT) can improve respiratory muscleweakness in chronic respiratory diseases. However , it is unclear whether RMT inducesadaptations in the respiratory center as well as respiratory muscles. We hypothesized therespiratory center in the medulla would also adapt to the RMT and less neurons became torecruit to achieve same minute ventilation under hypercapnic stimulation. T o clarify thishypothesis, the number of c-Fos positive medulllary neurons after short term hypercapnicstimulation (7%CO2, 50%O2, N2 balance, 90 min) in the rats with RMT was compared tothat in the untrained control rats. For the respiratory muscle training program, we usedthe hypercapnic stimulation that consisted of placing each rat in a hypercapnic chamberin order to increase the minute ventilation. The RMT rats (n=2) were placed in a chamberfilled with 7% CO2 and 50% O2 for 30 min, 5 times a week, for 4 weeks, whereas controlrats (n=2) were placed in the same chamber filled with room air . After 1.5 hours from thecompletion of the last trial of the 4 weeks program, axial sections from the medullaoblongata were processed for c-Fos immunohistochemistry .It was found that the number of the c-Fos positive neurons in the RMT rats were smallerthan those in the control rats at ventral and dorsal region of the medulla oblongata.