Regional distribution of the locomotor pattern-generating network in the neonatal rat spinal cord
Regional distribution of the locomotor pattern-generating network in the neonatal rat spinal cord
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DOI：
10.1152/jn.1997.77.1.247
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发表时间：
1997-01-01
影响因子：
2.5
通讯作者：
Schmidt, BJ
中科院分区：
文献类型：
--
作者：
Cowley, KC;Schmidt, BJ
用体外新生大鼠标本研究了产生运动性和非运动性活动的脊髓网络的区域分布。5-羟色胺(5-羟色胺)、乙酰胆碱(ACh)、N-甲基-D、L-天冬氨酸或联合应用5-羟色胺(5-HT)、乙酰胆碱(ACh)、N-甲基-D(N-甲基-D)、L-天冬氨酸(NMA)或联合应用均可诱发节律性活动，并通过后肢屈(腓)肌和伸(胫骨)肌神经电图(ENG)或腹根记录进行监测。在一些实验中，通过添加抑制性氨基酸(IAA)受体拮抗剂来产生同步模式。选择性地将5-羟色胺应用于颈、胸髓可引起这些节律性活动，但不能引起后肢ENG放电。将分离的腰椎区域暴露于5-羟色胺只能产生紧张性活动。将5-羟色胺应用于整个脊髓，在脊髓中矢状面从圆锥到胸腰交界处后，在后肢内侧产生持续的运动样活动。在其他实验中，在整个脊髓暴露于5-羟色胺的过程中，横断腰髓吻侧取消了同侧后肢引擎的节律性活动，这表明在这种情况下，腰髓一侧的节律性活动不足以维持对侧的节律性活动。选择性地将NMA或ACh应用于颈髓和/或胸髓区域，在这些腰上节段引起节律性活动，在腰部引起节律性但非运动性活动。与5-羟色胺的作用相反，NMA和ACh单独作用于腰部时均可诱发节律性活动，而全脊髓ACh引起的侧向交替不被腰部的矢状面正中病变所耦合。在IAA拮抗剂存在的情况下，尽管广泛的正中矢状面损伤使双侧颈、胸或腰髓的一段或两段完好无损，但双侧同步节律的侧侧耦合仍保持不变，即使在单个孤立的半节段也可以维持节律活动。5-羟色胺/NMA的作用与单独使用5-羟色胺的作用相似，但选择性地应用于前臂上区时，5-羟色胺/NMA可诱导后肢的节律性活动。结果表明：1)5-羟色胺敏感的振荡网络，能够产生运动样的活动模式，分布在脊髓的上半部，并介导向腰部运动中枢的下行节律性驱动；2)NMA和ACh敏感的节律性元件分布在整个脊髓，包括腰部；3)脊髓含有广泛的固有的相互抑制和兴奋联系的网络，其特点是冗余地组织两侧投射。
The regional distribution of spinal cord networks producing locomotor-like, as well as non-locomotor-like, activity was studied with the use of an in vitro neonatal rat preparation. Rhythmic activity was induced by bath application of either serotonin (5-HT), acetylcholine (ACh), N-methyl-D,L-aspartate (NMA), or combined 5-HT/NMA, and was monitored via hindlimb flexor (peroneal) and extensor (tibial) electroneurograms (ENGs) or ventral root recordings. In some experiments, synchronous patterns were produced by the addition of inhibitory amino acid (IAA) receptor antagonists. Selective application of 5-HT to cervical and thoracic cord regions induced rhythmic activity in these segments but failed to evoke hindlimb ENG discharge. Exposure of the isolated lumbar region to 5-HT produced tonic activity only. Application of 5-HT to the whole cord produced locomotor-like activity in hindlimb ENGs that persisted after midsagittal section of the spinal cord from the conus to the thoracolumbar junction. In other experiments, transverse hemisection of the rostral lumbar cord during whole cord exposure to 5-HT abolished rhythmic activity in ipsilateral hindlimb ENGs, suggesting that under these conditions rhythmic activity on one side of the lumbar cord was insufficient to maintain rhythmic activity on the contralateral side. Selective application of NMA or ACh to cervical and/or thoracic cord regions evoked rhythmic activity in these supralumbar segments, as well as rhythmic, but non-locomotor-like, activity in the lumbar region. In contrast to the effect of 5-HT, both NMA and ACh evoked rhythmic activity when applied solely to the lumbar region, and the side-to-side alternation produced by whole cord ACh application was uncoupled by midsagittal lesions of the lumbar region. In the presence of IAA antagonists, the side-to-side coupling of bilaterally synchronous rhythms was maintained despite extensive midsagittal lesions leaving all but one or two segments of either cervical, thoracic, or lumbar cord bilaterally intact, and rhythmic activity could be maintained even in single isolated hemisegments. The effects of 5-HT/NMA were similar to those observed with the use of 5-HT alone, although 5-HT/NMA induced rhythmic activity in hindlimb ENGs when applied selectively to supralumbar regions. The results suggest that 1) a 5-HT-sensitive oscillatory network, capable of producing a. locomotor-like pattern of activity, is distributed throughout the supralumbar region of the spinal cord and mediates descending rhythmic drive to lumbar motor centers; 2) NMA- and ACh-sensitive rhythmogenic elements are distributed throughout the spinal cord, including the lumbar region; and 3) the spinal cord contains an extensive propriospinal network of reciprocal inhibitory and excitatory connections characterized by redundantly organized side-to-side projections.