Changes in presynaptic inhibition of Ia fibres in man while standing.
Changes in presynaptic inhibition of Ia fibres in man while standing.
复制标题
人类站立时 Ia 纤维突触前抑制的变化。
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
Emmanuel Pierrot
中科院分区：
文献类型：
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作者：
R. Katz;Sabine Meunier;Emmanuel Pierrot
在相同的受试者中比较了无支持站立和对照情况（坐着或站着背部支持）时，对比目鱼肌、四头肌和胫前肌运动神经元的homoproteia传入终末和从四头肌到比目鱼肌的heteroproteia纤维的突触前抑制。Ia纤维突触前抑制的变化间接推导出的单突触Ia促进运动神经元引起的恒定的条件刺激的量的改变。在第一个0.5 ms时，单突触Ia兴奋性突触后电位（EPSP）尚未被污染的条件刺激诱发的多突触效应的促进。两种间接方法被用来提供的空调Ia EPSP的大小的估计：（1）所产生的H反射促进;（2）在自发激活的运动神经元引起的放电概率增加的峰值刺激homeprotein和hetereprotein Ia纤维（刺激后时间直方图PSTH方法）。只有那些PSTH实验中的运动单位的“自发”放电率是相同的，在不同的位置，从而确保一个相同的净突触驱动的运动神经元，被认为是。在这些条件下，它是假设的变化引起的单突触Ia齐射的促进峰的大小很可能是由Ia纤维的突触前抑制的变化。有人认为，单突触Ia兴奋时观察到的重大变化，站立没有支持可能反映突触前抑制Ia纤维的变化。在这种解释下，突触前抑制Ia纤维比目鱼肌运动神经元的增加，而站立没有支持，而突触前抑制homoprotein Ia纤维股四头肌运动神经元减少。没有证据表明Ia纤维对胫骨前运动神经元的突触前抑制发生了变化。由此产生的改变，这些肌肉的单突触反射的增益进行了讨论，在人类步态的单突触牵张反射的可能作用。
Presynaptic inhibition of homonymous Ia afferent terminals to soleus, quadriceps and tibialis anterior motoneurons and of heteronymous Ia fibres from quadriceps to soleus was compared in the same subjects when standing without support and during a control situation (sitting or standing with back support). Changes in presynaptic inhibition of Ia fibres were indirectly deduced from alterations in the amount of monosynaptic Ia facilitation elicited in motoneurons by a constant conditioning stimulation. Facilitation was measured during the first 0.5 ms when the monosynaptic Ia excitatory postsynaptic potential (EPSP) was not yet contaminated by polysynaptic effects evoked by the conditioning stimulation. Two indirect methods were used to provide an estimate of the size of the conditioning Ia EPSP: (1) the resulting H reflex facilitation; and (2) the peak of increased firing probability elicited in voluntarily activated motoneurons by stimulation of homonymous and heteronymous Ia fibres (poststimulus time histogram PSTH method). Only those PSTH experiments in which the 'spontaneous' firing rate of the motor unit was identical in the different positions, thus ensuring an identical net synaptic drive to the motoneuron, were considered. Under these conditions it is assumed that changes in the size of the peak of facilitation elicited by the monosynaptic Ia volley are likely to be caused by changes in presynaptic inhibition of Ia fibres. It is argued that the substantial changes in monosynaptic Ia excitation observed when standing without support probably reflect changes in presynaptic inhibition of Ia fibres. Under this interpretation, presynaptic inhibition of Ia fibres to soleus motoneurons is increased while standing without support, whereas presynaptic inhibition of homonymous Ia fibres to quadriceps motoneurons is decreased. There is no evidence for a change in presynaptic inhibition of Ia fibres to tibialis anterior motoneurons. The resulting alterations in the gain of the monosynaptic reflex of these muscles are discussed in relation to the possible role of the monosynaptic stretch reflex in human gait.