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目的 :研究兔膈肌肌条力学对不同频率慢性电刺激 (CES)的适应性变化特征和细胞外Ca2 +变化对其力学特征的影响。方法 :测定正常对照组和CES组的颤搐收缩张力 (Pt)、峰值张力时间 (TPT)、1/ 2松驰时间 (1/ 2RT)、强直颤搐收缩张力 (Po)、疲劳指数 (FI)和疲劳恢复指数 (FRI) ;观察在无Ca2 +Hank’s液和标准Hank’s液时肌条收缩张力消失和恢复的时间差异。结果 :①同对照组作比较 ,10Hz和 2 0Hz组的Pt、Po、Pt/Po明显降低 (P <0 .0 1) ,TPT和 1/ 2Rt明显延长 (P <0 .0 1) ,FI和FRI明显下降 (P <0 .0 1)。 5 0Hz和 10 0Hz组出现完全相反的效应 (P<0 .0 1)。②细胞外Ca2 +变化对CES各组肌条收缩张力的降低和恢复均有明显的影响 ,但以 10Hz和 2 0Hz组尤为显著 ,其收缩张力在较短的时间内明显降低 (P <0 .0 5 )。结论 :①膈肌肌条力学模式在不同频率CES后呈现出明显的频率依赖性 ;②细胞外Ca2 +变化对慢性低频电刺激后的膈肌肌条力学的影响明显增加
OBJECTIVE: To study the adaptive changes of rabbit diaphragm muscle strips mechanics to different frequencies of chronic electrical stimulation (CES) and the effects of extracellular Ca2 + changes on the mechanical characteristics. Methods: The twitch tension (Pt), peak tonic time (TPT), 1/2 relaxation time (1 / 2RT), tonic tonic contraction (Po) and fatigue index (FI) were measured in normal control group and CES group ) And fatigue recovery index (FRI). The difference in time between disappearance and recovery of contractile tension of muscle strips in the absence of Ca2 + Hank’s solution and standard Hank’s solution was observed. Results: ①Compared with the control group, Pt, Po, Pt / Po in 10 Hz and 20 Hz groups were significantly decreased (P <0.01), TPT and 1 / 2Rt were significantly prolonged And FRI decreased significantly (P <0.01). The exact opposite effect was observed for the 5 0 Hz and 10 0 Hz groups (P <0.01). (2) The change of extracellular Ca2 + had a significant effect on the reduction and recovery of contractile tension in CES muscle strips, especially at 10Hz and 20Hz, the contractile tension decreased obviously in a short time (P <0. 0 5). Conclusion: (1) Mechanical model of diaphragmatic muscle strips showed obvious frequency dependence after CES at different frequencies. (2) Changes of extracellular Ca2 + significantly affected the mechanics of diaphragmatic muscle strips after chronic low frequency electrical stimulation