Nonlinear summation of contractions in cat muscles. II. Later facilitation and stiffness changes.
Nonlinear summation of contractions in cat muscles. II. Later facilitation and stiffness changes.
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DOI：
10.1085/jgp.78.3.295
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发表时间：
1981-09
影响因子：
3.8
通讯作者：
Stein, R B
中科院分区：
文献类型：
--
作者：
Parmiggiani, F;Stein, R B
猫的肌肉随着时间的推移，在间隔很短的时间间隔的两次刺激下产生的力大约是猫肌肉抽搐产生的力的三倍。通过第二次刺激促进力的产生涉及收缩幅度和持续时间的增加。增加幅度对于快肌跖肌相对更重要，而增加持续时间对于慢肌比目鱼肌更重要。随着刺激之间的间隔，促进作用以近似指数的方式衰减，时间常数在不同肌肉抽搐收缩时间的一到两倍之间。如果添加第三个刺激，则在比抽搐收缩时间更长的时间间隔内会看到最大的促进作用。药物丹曲林（Dantrolene）专门减少肌浆网中 Ca++ 的释放，消除了三种刺激促进中的延迟峰值。与一种或多种刺激力的增加相关的是肌肉僵硬的增加，这可以通过不改变收缩时程的小而短暂的拉伸和释放来测量。比目鱼肌的僵硬在力达到峰值后达到峰值。除了 Ca++ 释放机制产生的任何促进作用之外，肌肉硬度的增加还可以极大地促进内部产生的力的传递。
The force produced by cat muscles over time with two stimuli separated by a short interval is approximately three times that produced by a twitch of cat muscles. This facilitation of force production by a second stimulus involves both increases in magnitude and duration of the contraction. Increased magnitude is relatively more important in the fast-twitch plantaris muscle, whereas increased duration is more important in the slow-twitch soleus muscle. The facilitation decays in an approximately exponential manner with the interval between stimuli, having a time constant between one and two times the twitch contraction time in different muscles. If a third stimulus is added, the greatest facilitation is seen at intervals longer than the twitch contraction time. The drug Dantrolene, which specifically reduces Ca++ release from the sarcoplasmic reticulum, eliminates the delayed peak in facilitation with three stimuli. Associated with the increases in force with one or more stimuli are increases in muscle stiffness, which can be measured with small, brief stretches and releases that do not alter the time- course of contraction. The stiffness of soleus muscle reaches a peak after the peak in force. The increasing stiffness of the muscle can considerably facilitate transmission of force generated internally, in addition to any facilitation arising from Ca++-release mechanisms.