兔膈肌力学模式对慢性电刺激的适应性改变和细胞外Ca …

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Ｃａ＾２＋变化夺其力学特征的影响。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松弛时间（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Ｃａ＾２＋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，

Adaptation of diaphragm muscle strip mechanics to chronic electrical stimulation and the effect of change in extracellular Ca2+ in rabbit]

AIM: The mechanical character of diaphragm muscle after chronic electrical stimulation(CES) and effect of the extracellular Ca2+ change have not yet been explored. We wondered whether there might be great different change and effect on muscle mechanics after CES and the extracellular Ca2+ change. METHODS: The twitch tension(Pt), time to peak tension(TPT), half-relaxation time(1/2 RT), tetanic tension(Po), fatigue index (FI) and fatigue recovery index(FRI) were respectively measured in normal group and CES groups; the switch tensions of diaphragm muscle strips were observed in the standard Hank's solution and the Hank's with free Ca2+. RESULTS: There were more significant decrease in Pt, Po, FI and FRI, more significant lengthening in TPT and 1/2 RT in 10 Hz and 20 Hz groups(P < 0.01). However, there was completely opposite effect in 50 Hz and 100 Hz groups. There were more significant effect on muscle mechanics of contraction and relaxation in 10 Hz and 20 Hz groups than that in 50 Hz and 100 Hz groups when the extracellular Ca2+ changed. CONCLUSION: After CES the significantly frequency dependent were presented on mechanical character of diaphragm muscle strips, and there were more effect on diaphragm muscle mechanics in 10 Hz and 20 Hz groups when the extracellular Ca2+ was changed.