REFLEX RESPONSES OF GAMMA MOTONEURONS TO VIBRATION OF MUSCLE THEY INNERVATE
REFLEX RESPONSES OF GAMMA MOTONEURONS TO VIBRATION OF MUSCLE THEY INNERVATE
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DOI：
10.1113/jphysiol.1976.sp011315
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发表时间：
1976-01-01
影响因子：
5.5
通讯作者：
NOTH, J
中科院分区：
文献类型：
--
作者：
FROMM, C;NOTH, J
1.对非收缩性小腿三头肌的肌腱施加高频振动，同时记录单根伽马纤维的背景放电，仅切割小神经束，保留大部分三头肌的神经供应完整。2.在总共63个伽马传出神经中，有22%受到振动的紧张性抑制。抑制出现在25和50 μ m峰间振幅的振动之间，并在振幅约为100 μ m时增加到平台。α传出神经的强直性振动反射对振动幅度的依赖性被发现是相似的。将振动频率从150 Hz增加到300 Hz，抑制程度增加。3. 33%的梭运动神经元对肌肉振动有反应，放电率增加。该反射的阈值幅度范围为20 - 50 μ m。反射的一些特征，特别是在α和γ传出神经中发现的平行振动后易化，指出了在α-γ连接中组织的多突触通路。4.振动抑制的所有γ传出神经对刺激前根的逆向反应均表现出抑制作用，其中大部分被肱三头肌的斜坡牵拉所抑制。然而，振动促进的γ运动神经元在肌肉拉伸时兴奋，对逆向抑制不太敏感，有些完全没有。5.切断三头肌的神经消除了γ传出神经对肌肉振动的抑制性和兴奋性反应。在脊髓切片和随后给予L-DOPA后，两种梭动反射均得以保留。6.结论：振动的两种梭运动反射效应都是由肱三头肌内初级梭末梢的兴奋引起的。梭运动神经元的抑制被认为是由振动期间激活的Renshaw细胞介导的。正反馈对γ运动神经元作为Ia传入的自生易化的结果的意义与牵张反射回路的稳定性一起讨论。
1. High frequency vibration was applied to the tendon of the non‐contracting triceps surae muscle while recording the background discharges of single gamma fibres only small nerve bundles were cut, leaving most of the nerve supply to the triceps intact. 2. 22% out of a total of sixty‐three gamma efferents were tonically inhibited by vibration. The inhibition appeared between 25 and 50mum peak‐to‐peak amplitude of vibration and increased to a plateau for amplitudes of about 100mum. The dependence of the tonic vibration reflex of alpha‐efferents on the amplitude of vibration was found to be similar. Increasing the frequency of vibration from 150 to 300 Hz increased the degree of inhibition. 3. 33% of the fusimotor neurones investigated responded to muscle vibration with an increase in discharge rate. The threshold amplitudes of this reflex ranged from 20 to 50mum. Some features of the reflex, in particular the parallel post‐vibratory facilitation found in alpha and gamma efferents, pointed to a polysynaptic pathway organized in an alpha‐gamma linkage. 4. All gamma efferents inhibited by vibration showed inhibitory responses to antidromic stimulation of the parent ventral root, and most of them were inhibited by ramp stretch of the triceps. The gamma motoneurones facilitated by vibration, however, were excited by muscle stretch and were less susceptible to antidromic inhibition, some lacking it completely. 5. Cutting the nerves to triceps abolished the inhibitory as well as the excitatory responses of gamma efferents to muscle vibration. Both fusimotor reflexes were preserved after spinal section and subsequent administration of L‐DOPA. 6. It is concluded that both of the fusimotor reflex effects of vibration are caused by excitation of primary spindle endings within the triceps. The inhibition of fusimotor neurones is thought to be mediated by Renshaw cells activated during vibration. The significance of positive feed‐back on to gamma motoneurones as a result of autogenetic facilitation by Ia afferents is discussed in connexion with stability in the stretch reflex loop.