Activity of hindlimb motor units during locomotion in the conscious rat
Activity of hindlimb motor units during locomotion in the conscious rat
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DOI：
10.1152/jn.2000.83.4.2002
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发表时间：
2000-04-01
影响因子：
2.5
通讯作者：
Hultborn, H
中科院分区：
文献类型：
--
作者：
Gorassini, M;Eken, T;Hultborn, H
本文比较了清醒大鼠在自由行走过程中，主要由快缩肌纤维组成的肌肉（内侧和外侧腓肠肌：MG/LG，胫骨前肌：TA）和主要由慢缩肌纤维组成的肌肉（比目鱼肌：SOL）的后肢运动单位的活动。从这两组肌肉的运动单位的激活配置文件中的几个差异进行了观察。例如，来自快速肌肉的运动单位（例如，MG/LG和TA）以非常高的平均放电频率（范围从60到100 Hz）发射，并且几乎总是以初始双峰或三峰募集，即，初始频率大于或等于100 Hz。相比之下，大多数SOL单元以低得多的平均放电速率发射，接近30 Hz，并且具有仅30-60 Hz的初始频率（即，不存在大于或等于100 Hz的初始双峰/三联峰）。因此，初始双联体或三联体的存在取决于运动单位的内在性质，即，与较慢的单位相比，较快的单位更经常地被招募为具有双联体/三联体。此外，在相反的单位从慢速SOL肌肉，单运动单位的活动从快速MG/LG肌肉，特别是单位招募中途或接近年底的运动爆发，是无关的活动的其余部分的运动神经元池，测量相应的总肌电图（EMG）信号。这种活动的解离被认为是由脊髓的节律产生网络对MG/LG运动神经元池的区室化募集引起的。相比之下，当比较在一个单一的LG肌肉室同时记录的运动单位的速率调制，单位对的频率分布调制在一个平行的方式。这表明，父母运动神经元在无限制的步行过程中对突触输入的变化作出反应，而不像脑干刺激诱导的运动过程中发生的差的速率调制。总之，从这项研究的数据提供的证据表明，在不受限制的步行运动单位的发射行为的影响，既有内在的属性的父母运动神经元和突触输入的运动网络的脊髓。此外，它还提供了第一个广泛的描述运动单位的活动，从不同的肌肉在无约束的行走在清醒的大鼠。
This paper compares the activity of hindlimb motor units from muscles mainly composed of fast-twitch muscle fibers (medial and lateral gastroenemius: MG/LG, tibialis anterior: TA) to motor units from a muscle mainly composed of slow-twitch muscle fibers (soleus: SOL) during unrestrained walking in the conscious rat. Several differences in the activation profiles of motor units from these two groups of muscles were observed. For example, motor units from fast muscles (e.g., MG/LG and TA) fired at very high mean frequencies of discharge, ranging from 60 to 100 Hz, and almost always were recruited with initial doublets or triplets, i.e., initial frequencies greater than or equal to 100 Hz. In contrast, the majority of SOL units fired at much lower mean rates of discharge, approximate to 30 Hz, and had initial frequencies of only 30-60 Hz (i.e., there were no initial doublets/triplets greater than or equal to 100 Hz). Thus the presence of initial doublet or triplets was dependent on the intrinsic properties of the motor unit, i.e., faster units were recruited with a doublet/triplet more often than slower units. Moreover, in contrast to units from the slow SOL muscle, the activity of single motor units from the fast MG/LG muscle, especially units recruited midway or near the end of a locomotor burst, was unrelated to the activity of the remainder of the motoneuron pool, as measured by the corresponding gross-electromyographic (EMG) signal. This dissociation of activity was suggested to arise from a compartmentalized recruitment of the MG/LG motoneuron pool by the rhythm-generating networks of the spinal cord. In contrast, when comparing the rate modulation of simultaneously recorded motor units within a single LG muscle compartment, the frequency profiles of unit pairs were modulated in a parallel fashion. This suggested that the parent motoneurons were responsive to changes in synaptic inputs during unrestrained walking, unlike the poor rate modulation that occurs during locomotion induced from brain stem stimulation. In summary, data from this study provide evidence that the firing behavior of motor units during unrestrained walking is influenced by both the intrinsic properties of the parent motoneuron and by synaptic inputs from the locomotor networks of the spinal cord. in addition, it also provides the first extensive description of motor-unit activity from different muscles during unrestrained walking in the conscious rat.