Age related functional and morphological alterations in rat diaphragm and phrenic motoneuron

招募的膈运动神经元的所有参数均无显著差异，而未招募的运动神经元的基础值在2年组显著低于其他两组。1、2年龄运动神经元的平均动作电位间期均长于10周龄组，2年龄组的放电模式明显不规则。虽然各组间的抽动张力无显著差异，但高频刺激(20-100 Hz)引起的破伤风张力在老年组显著降低。老年横隔肌的张力达峰时间和半松弛时间明显延长。组织化学结果显示，老年横隔肌FG纤维面积较小，SO纤维所占比例较高。

No significant differences were found in all parameters in recruited phrenic motoneuron, while the rheobase of the non-recruited motoneurons was significantly lower in the 2-year group than the other two groups. The mean interval of action potentials of the recruited motoneurons was longer in the 1- and 2-year groups than the 10-week group, and the firing pattern in 2-year group was considerably irregular. Although there were no significant differences in the twitch tension among the groups, tetanus tensions by high frequency stimulation (20-100Hz) were significantly lower in the older group. The time to peak tension and half relaxation time were significantly longer in aged diaphragm muscles. The histochemical profiles of aged diaphragm muscle showed a smaller area of FG fibers and higher percentage of SO fibers.