Nichols T R, Steeves J D
Exp Brain Res. 1986;62(2):401-10. doi: 10.1007/BF00238859.
Flexor (tibialis anterior, TA, and extensor digitorum longus, EDL) and extensor (soleus, SOL) muscles in the decerebrate cat were subjected to length changes and the force responses were measured. Resultant muscular stiffness, which arises from the mechanical reaction of muscle fibers contracting prior to the length change and from a change in force due to reflex action, was calculated by dividing the changes in force by the corresponding length changes. As shown previously in the premammillary preparation, resultant stiffness was usually higher in SOL than in TA or EDL. Following an intercollicular transection in some preparations, resultant stiffness increased markedly for TA but not substantially for SOL. During continuous electrical stimulation in the magnocellular red nucleus in premammillary preparations, resultant stiffness of SOL decreased for a wide range of forces while EDL responses were unaffected. These results show that reflex gain is not determined solely by the level of motoneuronal excitability but also by a descending control from the brainstem, and that the lower resultant stiffness in flexors compared to extensors in the decerebrate cat is set by this control system and not by inherent differences in the strength of autogenetic reflex pathways for the two muscles.
对去大脑猫的屈肌（胫骨前肌、TA和趾长伸肌、EDL）和伸肌（比目鱼肌、SOL）进行长度改变，并测量其力反应。通过将力的变化除以相应的长度变化来计算合成肌肉刚度，合成肌肉刚度源于长度变化之前收缩的肌肉纤维的机械反应以及反射作用引起的力的变化。如先前在乳头前制备中所示，SOL的合成刚度通常高于TA或EDL。在一些制备中进行间脑横断后，TA的合成刚度显著增加，而SOL的合成刚度基本不变。在乳头前制备中对大细胞红核进行连续电刺激期间，在很宽的力范围内，SOL的合成刚度降低，而EDL的反应不受影响。这些结果表明，反射增益不仅取决于运动神经元的兴奋性水平，还取决于来自脑干的下行控制，并且去大脑猫中屈肌与伸肌相比较低的合成刚度是由该控制系统设定的，而不是由这两块肌肉的自生反射通路强度的固有差异所决定的。
