Proske U, Gregory J E, Morgan D L
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Exp Physiol. 1991 Sep;76(5):777-85. doi: 10.1113/expphysiol.1991.sp003543.
This is a report of experiments on muscle spindles of the soleus muscle of the anaesthetized cat. Following a step shortening of the muscle, muscle spindles fall silent. At suitable muscle lengths their discharge may restart several seconds later to gradually recover a maintained rate of discharge. These experiments examine the question of where within the spindle the resumption of a resting discharge may originate. It was found that stimulation of some static fusimotor fibres immediately after the shortening led to early recovery of the resting discharge. Stimulation of dynamic and other static gamma motoneurones had much less effect. Since the dynamic gamma axons innervate almost exclusively the bag1 intrafusal fibre, contraction of this fibre appears to have little influence on the mechanisms responsible for restarting the resting discharge. Bag2 and chain fibres do seem to be involved. For primary endings, the bag2 fibre contraction was especially effective since static axons, which did not evoke 'driving' of the afferent response, and which are thought to predominantly innervate bag2 fibres, did restart the resting discharge. For secondary endings, stimulation of nearly all gamma axons led to an early restart of the resting discharge suggesting that here the nuclear chain fibres were responsible.
这是一篇关于对麻醉猫比目鱼肌肌梭进行实验的报告。在肌肉进行阶跃式缩短后，肌梭停止放电。在合适的肌肉长度下，它们的放电可能在几秒钟后重新开始，并逐渐恢复到维持的放电频率。这些实验探讨了静息放电恢复可能起源于肌梭内何处的问题。研究发现，在缩短后立即刺激一些静态梭内肌纤维会导致静息放电提前恢复。刺激动态和其他静态γ运动神经元的效果则小得多。由于动态γ轴突几乎只支配袋1类核袋纤维，该纤维的收缩似乎对负责重新开始静息放电的机制影响很小。袋2类纤维和连锁纤维似乎确实参与其中。对于初级末梢，袋2类纤维收缩特别有效，因为那些不会引起传入反应“驱动”且被认为主要支配袋2类纤维的静态轴突确实能重新开始静息放电。对于次级末梢，几乎所有γ轴突的刺激都会导致静息放电提前重新开始，这表明在此处核连锁纤维起了作用。
