Boyd I A
Q J Exp Physiol. 1986 Apr;71(2):307-27. doi: 10.1113/expphysiol.1986.sp002987.
The action of single static gamma-axons in 'single fibre' ventral root filaments was tested on the responses of from two to eight spindles in the same tenuissimus muscle in anaesthetized cats. The type of intrafusal fibre activated in each spindle by a particular axon was diagnosed from its effect on the discharge of primary and secondary sensory endings, frequently in the same spindle. One or two spindles were subsequently isolated in most experiments and the type of intrafusal fibre activated by the axon was observed directly. Except in the case of a few weak actions which could not be interpreted, the diagnosis made from the afferent recordings was always correct. Twenty-four static gamma-axons activated the chain fibres in every spindle they supplied on which their action was tested; the static bag2 fibre was also involved in about 20% of the spindles though its contraction was quite often weak. Eleven static gamma-axons activated the static bag2 fibre in every spindle they supplied on which their action was tested; some chain fibres were activated as well in about 20% of the spindles. There were only two possible exceptions to the general rule that a static gamma-axon activates either the chain fibres or the static bag2 fibre in every spindle it supplies and never activates only the chain fibres in one spindle, and only the static bag2 fibre in another spindle. Direct observation of isolated spindles provided preliminary evidence that some non-selective connexions of static gamma-axons have a pronounced physiological action by way of their terminals on one type of intrafusal fibre while the terminal(s) on the other type of fibre produce such a weak contraction that the sensory endings are not affected. Other non-selective connexions do, however, have a significant physiological effect by way of their terminals on both the static bag2 fibre and the chain fibres. It is proposed that there are two types of static gamma-motoneurone. 'Static bag gamma-motoneurones', through their terminals on the static bag2 fibre in every spindle, bias the discharge from primary endings (and to a lesser extent from some secondary endings) but leave their length sensitivity largely unaltered; connexions to chain fibres in some spindles have a weak action on primary endings but may greatly increase the length sensitivity of secondary endings.(ABSTRACT TRUNCATED AT 400 WORDS)
在麻醉猫的同一薄肌中，测试了单根静态γ运动轴突在“单纤维”腹根细丝中的作用对两到八个肌梭反应的影响。根据特定轴突对每个肌梭中初级和次级感觉末梢放电的影响（通常在同一个肌梭中），来判断该轴突激活的肌梭内纤维类型。在大多数实验中，随后分离出一两个肌梭，并直接观察轴突激活的肌梭内纤维类型。除了少数无法解释的微弱作用外，根据传入记录做出的诊断总是正确的。24根静态γ运动轴突激活了它们所支配且接受测试的每个肌梭中的串联纤维；静态袋2纤维也参与了约20%的肌梭活动，不过其收缩往往较弱。11根静态γ运动轴突激活了它们所支配且接受测试的每个肌梭中的静态袋2纤维；在约20%的肌梭中，一些串联纤维也被激活。一般规则是，静态γ运动轴突在其支配的每个肌梭中要么激活串联纤维，要么激活静态袋2纤维，且从不只在一个肌梭中激活串联纤维，而在另一个肌梭中只激活静态袋2纤维，只有两个可能的例外情况。对分离肌梭的直接观察提供了初步证据，表明一些静态γ运动轴突的非选择性连接通过其在一种肌梭内纤维上的终末具有明显的生理作用，而在另一种纤维上的终末产生的收缩非常弱，以至于感觉末梢不受影响。然而，其他非选择性连接通过其在静态袋2纤维和串联纤维上的终末确实具有显著的生理效应。有人提出存在两种类型的静态γ运动神经元。“静态袋γ运动神经元”通过其在每个肌梭中静态袋2纤维上的终末，使初级末梢（以及在较小程度上使一些次级末梢）的放电产生偏差，但在很大程度上保持其长度敏感性不变；在一些肌梭中与串联纤维的连接对初级末梢有微弱作用，但可能大大增加次级末梢的长度敏感性。（摘要截断于400字）
