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是否诱导呼吸中枢以及呼吸肌的适应。我们假设延髓的呼吸中枢也会适应RMT，在高碳酸刺激下，更少的神经元开始募集以达到相同的每分钟通气量。为阐明这一假说，我们比较了短期高二氧化碳刺激（7%CO_2，50%O_2，N_2平衡，90 min）后RMT大鼠和未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，我们使用高碳酸刺激，包括将每只大鼠置于高碳酸室中以增加每分钟通气量。将RMT大鼠（n=2）置于7%CO_2和50%O_2的空气室中30 min，每周5次，连续4周，对照组大鼠（n=2）置于相同的空气室中。最后一次实验结束后1.5小时取延髓轴位切片，进行c-Fos免疫组织化学染色，结果发现，在延髓腹侧和背侧，RMT组大鼠的c-Fos阳性神经元数量明显少于对照组。

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.