Stein R B, Parmiggiani F
J Gen Physiol. 1981 Sep;78(3):277-93. doi: 10.1085/jgp.78.3.277.
Nerves to fast- and slow-twitch cat muscles were stimulated with various numbers of supramaximal pulses under isometric conditions. By subtracting the force produced by j - 1 pulses from that produced by j pulses, the contribution of the j th pulse could be compared with the response to one pulse (twitch response). A less-than-linear summation (depression) was observed during the rising phase of the twitch. This depression became increasingly prominent and longer in duration with repetitive stimulation. A more-than-linear summation (facilitation) was observed during the falling phase of the twitch, which became increasingly delayed and smaller in amplitude with repetitive stimulation. The early depression could be abolished for the first few pulses by Dantrolene [1-(5-p-nitrophenyl) furfurilidene amino hydantoin sodium hydrate], which reduced Ca++ release from the sarcoplasmic reticulum. The depression was less prominent at short muscle lengths or with stimulation of single motor units. A first-order, saturable reaction such as Ca++ binding to troponin or actin binding to myosin can quantitatively account for the early depression.
在等长条件下，用不同数量的超强脉冲刺激猫的快肌和慢肌神经。通过用j个脉冲产生的力减去j - 1个脉冲产生的力，可以将第j个脉冲的贡献与对单个脉冲的反应（抽搐反应）进行比较。在抽搐的上升阶段观察到小于线性的总和（抑制）。随着重复刺激，这种抑制变得越来越明显且持续时间更长。在抽搐的下降阶段观察到大于线性的总和（易化），随着重复刺激，其延迟越来越大且幅度越来越小。丹曲林[1 - (5 - 对硝基苯基)糠叉氨基乙内酰脲水合物]可在最初几个脉冲时消除早期抑制，它减少了肌浆网中钙离子的释放。在短肌肉长度或刺激单个运动单位时，抑制不太明显。像钙离子与肌钙蛋白结合或肌动蛋白与肌球蛋白结合这样的一级饱和反应可以定量解释早期抑制。
