FUNCTIONAL-ORGANIZATION WITHIN THE MEDULLARY RETICULAR-FORMATION OF THE INTACT UNANESTHETIZED CAT .3. MICROSTIMULATION DURING LOCOMOTION
FUNCTIONAL-ORGANIZATION WITHIN THE MEDULLARY RETICULAR-FORMATION OF THE INTACT UNANESTHETIZED CAT .3. MICROSTIMULATION DURING LOCOMOTION
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DOI：
10.1152/jn.1991.66.3.919
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发表时间：
1991-09-01
影响因子：
2.5
通讯作者：
DREW, T
中科院分区：
文献类型：
--
作者：
DREW, T
1. 本文介绍了四只未麻醉的完整猫在运动过程中对髓质网状结构（MRF；距离中线 0.5 至 2.5 毫米）内的 21 个位点和内侧纵束 (MLF) 中的 5 个位点进行刺激的结果。刺激序列（I 1 脉冲，持续时间 0.2 毫秒，330 Hz，刺激强度 35-mu-A）应用于每个轨迹中的那些位点，在这些位点上，猫休息时四个肢体中的每一个都获得了最广泛的影响。记录各肢屈肌、伸肌的肌电图。2．正如之前报道的，对休息时的猫进行刺激通常会在不止一只肢体的屈肌和伸肌中引起短暂的、短潜伏期的抽搐反应。相反，运动过程中的刺激会引起更复杂的活动模式，其中通常在一对或另一对肌肉中引起反应并纳入运动模式。3。在大多数部位，在每块肌肉自然活跃的步伐周期期间，刺激都会在四个肢体的屈肌中引起兴奋反应；运动站立阶段的刺激虽然效果较差，但也能够在这些肌肉中产生反应。研究的所有三块同侧伸肌[三头肌和股外侧肌的长头和外侧头（分别为 Tri、TriL 和 VL）] 在肌肉活动阶段通常受到抑制，尽管偶尔会看到兴奋反应。对侧 (co) Tri 的反应始终是兴奋性的，并且在肌肉活动期间最大，而 coVL 活动期间的反应是混合的，从任何一个位点都可以看到兴奋性和抑制性反应。 4．当在运动周期期间肌肉活跃期间施加刺激时，兴奋反应通常最大。当肌肉不活动时引起的反应有时比动物休息时引起的反应更大；这种反应最常见于后肢屈肌和 co VL.5。在四个肢体的屈肌和伸肌中，当猫休息时，反应潜伏期最长，而在相应肌肉活动期间给予的刺激则反应潜伏期最短。肌肉活动期间的平均潜伏期范围从同侧 Tri 和 TriL 抑制反应的最小 9.0 +/- 2.6 (SD) ms 到同侧半腱肌诱发反应的最大 17.1 +/- 3.0 ms。6．传递到前后平面（P3.1-9.7）中不同位点的刺激通常会引起与反应符号（兴奋或抑制）以及在任何一块肌肉中观察到最大效果的步进周期周期相似的反应。然而，来自不同位点的任何一块肌肉所引起的反应的相对幅度存在差异。7。刺激 MRF 和 MLF 引起的反应在大多数方面都是相似的。然而，对于 MLF 内传递的刺激，屈肌反应的相对幅度总是大于 MRF 内传递的刺激。两个不同区域的伸肌反应幅度通常相似。8．结果表明，当猫行走时，MRF 与其目标运动神经元之间的功能连接发生了变化。这似乎主要是由于中间神经元兴奋性水平的差异变化所致，中间神经元可能是运动中枢模式发生器（CPG）的一部分或由其驱动。在一些肌肉中，这些效应被认为是通过兴奋性和抑制性中间神经元介导的，刺激的最终表达取决于施加刺激的步骤周期的阶段。9。有人认为，已知的单个网状脊髓轴突的分支模式提供了一种基础，神经系统可以同时影响多个肢体的肌肉活动。讨论了 CPG 在协调不同肢体的这些反应中的作用。
1. This article presents the results from stimulation in 21 loci within the medullary reticular formation (MRF; between 0.5 and 2.5 mm from the midline) and in 5 loci in the medial longitudinal fasciculus (MLF) of four intact, unanesthetized cats during locomotion. Stimulus trains (I 1 pulses, 0.2-ms duration, 330 Hz, stimulus strength 35-mu-A) were applied at those loci in each track at which the most widespread effects in each of the four limbs were obtained with the cat at rest. Electromyograms were recorded from flexor and extensor muscles of each limb.2. As previously reported, stimulation with the cat at rest generally evoked brief, short-latency, twitch responses in both flexor and extensor muscles of more than one limb. In contrast, stimulation during locomotion evoked a more complex pattern of activity in which responses were normally evoked in one or other of the muscle pairs and incorporated into the locomotor pattern.3. In the majority of sites, the stimulation evoked excitatory responses in the flexor muscles of each of the four limbs during that period of the step cycle in which each respective muscle was naturally active; stimulation in the stance phase of locomotion, although less effective, was also capable of producing responses in these muscles. All three ipsilateral extensor muscles studied [long and lateral heads of triceps and vastus lateralis (Tri, TriL, and VL, respectively)] were normally inhibited during their phase of muscle activity, although excitatory responses were occasionally seen. Responses in the contralateral (co) Tri were invariably excitatory and were largest during the period of muscle activity, whereas responses during the period of activity of the coVL were mixed, with both excitatory and inhibitory responses being seen from any one locus.4. Excitatory responses were normally largest when stimulation was applied during the time that the muscle was active during the locomotor cycle. Responses evoked at times when the muscle was inactive were sometimes larger than those evoked with the animal at rest; such responses were most commonly seen in the hindlimb flexors and in the co VL.5. In both flexors and extensors of each of the four limbs, the latency of the responses was greatest when the cat was at rest and least for stimuli given during the period of activity of the respective muscle. Average latencies during the period of muscle activity ranged from a minimum of 9.0 +/- 2.6 (SD) ms for inhibitory responses in the ipsilateral Tri and TriL to a maximum of 17.1 +/- 3.0 ms for the responses evoked in the ipsilateral semitendinosus.6. Stimuli delivered to different loci in the anteroposterior plane (P3.1-9.7) generally evoked responses that were similar with respect to the sign of the response (excitation or inhibition) and to the period of the step cycle in which the maximal effect in any one muscle was observed. Differences occurred, however, in the relative amplitude of the response evoked in any one muscle from different loci.7. The responses evoked by stimulation of the MRF and the MLF were similar in most respects. The relative amplitude of the responses in flexor muscles, however, was always greater for stimuli delivered within the MLF than in the MRF. The amplitude of the responses in the extensor muscles were generally similar for the two different regions.8. The results suggest that there is a change in the functional connections between the MRF and its target motoneurons when the cat walks. This appears to be due principally to differential changes in the level of excitability of interneurons which are probably either part of, or driven by, the central pattern generator (CPG) for locomotion. In some muscles the effects are suggested to be mediated through both excitatory and inhibitory interneurons, with the final expression of the stimulation being dependent on the phase of the step cycle in which the stimulus is applied.9. It is suggested that the known branching pattern of individual reticulospinal axons provides a substrate whereby the nervous system may simultaneously affect the activity of muscles of more than one limb. The role of the CPG in coordinating these responses in the different limbs is discussed.