Properties of rhythmic activity generated by the isolated spinal cord of the neonatal mouse
Properties of rhythmic activity generated by the isolated spinal cord of the neonatal mouse
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DOI：
10.1152/jn.2000.84.6.2821
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发表时间：
2000-12-01
影响因子：
2.5
通讯作者：
O'Donovan, MJ
中科院分区：
文献类型：
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作者：
Whelan, P;Bonnot, A;O'Donovan, MJ
我们检查了新生小鼠（P0-7）的离体腰骶脊髓在几种不同条件下产生节律性运动活动的能力。在没有电刺激或药理刺激的情况下，我们记录了几种自发腹侧根去极化和放电的模式。对侧腹根之间的自发、交替放电可能在 10 分钟的间隔内发生 2 至 3 次。我们还观察到其他模式，包括左右同步和仅限于绳索一侧的节律活动。传递到腰椎/尾骨背根或腓肠神经的刺激序列可靠地诱发节律活动的发作。在这些诱发事件期间，有节律的腹侧根放电可能发生在脊髓的一侧，或者可能从一侧交替到另一侧。使用 N-甲基-D,L-天冬氨酸 (NMA)、血清素和多巴胺组合进行沐浴，可产生可持续数小时的节律性活动。在这些条件下，从左、右L-1-L-3腹根交替记录放电。在L-4-L-5段中，每个周期中的放电有两个峰值，与同侧和对侧L-1-L-3根的放电一致。 L-6 腹侧根放电与同侧 L-1-L-3 根记录的放电交替。通过记录同侧后肢屈肌和伸肌神经之间的交替放电模式，我们确定药物诱导的节律是类似运动的。此外，通过同时记录腹根和肌肉神经，我们确定踝关节屈肌放电与同侧L-1/L-2腹根放电同相，而伸肌放电与同侧L6腹根放电同相。脊髓中矢状切片后，腹侧根放电的节律模式得以保留，这表明脊髓左右两侧之间的相互抑制连接对于新生小鼠脊髓的节律发生并不是必需的。在完整和半切的制剂中阻断 N-甲基-D-天冬氨酸受体表明，这些受体对节律发生有贡献，但不是必需的。相反，用 6-cyano-7-硝基喹喔啉-2,3-二酮阻断红藻氨酸/AMPA 受体后，节律被取消。这些发现表明，分离的小鼠脊髓可以产生多种协调活动，包括类似运动的活动。在各种不同条件下研究这些行为的能力为未来研究该制剂中的节律发生机制提供了希望。
We examined the ability of the isolated lumbosacral spinal cord of the neonatal mouse (P0-7) to generate rhythmic motor activity under several different conditions. In the absence of electrical or pharmacological stimulation, we recorded several patterns of spontaneous ventral root depolarization and discharge. Spontaneous, alternating discharge between contralateral ventral roots could occur two to three times over a 10-min interval. We also observed other patterns, including left-right synchrony and rhythmic activity restricted to one side of the cord. Trains of stimuli delivered to the lumbar/coccygeal dorsal roots or the sural nerve reliably evoked episodes of rhythmic activity. During these evoked episodes, rhythmic ventral root discharges could occur on one side of the cord or could alternate from side to side. Bath application of a combination of N-methyl-D,L-aspartate (NMA), serotonin, and dopamine produced rhythmic activity that could last for several hours. Under these conditions, the discharge recorded from the left and right L-1-L-3 ventral roots alternated. In the L-4-L-5 segments, the discharge had two peaks in each cycle, coincident with discharge of the ipsilateral and contralateral L-1-L-3 roots. The L-6 ventral root discharge alternated with that recorded from the ipsilateral L-1-L-3 roots. We established that the drug-induced rhythm was locomotor-like by recording an alternating pattern of discharge between ipsilateral flexor and extensor hindlimb muscle nerves. In addition, by recording simultaneously from ventral roots and muscle nerves, we established that ankle flexor discharge was in phase with ipsilateral L-1/L-2 ventral root discharge, while extensor discharge was in phase with ipsilateral L6 ventral root discharge. Rhythmic patterns of ventral root discharge were preserved following mid-sagittal section of the spinal cord, demonstrating that reciprocal inhibitory connections between the left and right sides of the cord are not essential for rhythmogenesis in the neonatal mouse cord. Blocking N-methyl-D-aspartate receptors, in both the intact and the hemisected preparation, revealed that these receptors contribute to but are not essential for rhythmogenesis. In contrast, the rhythm was abolished following blockade of kainate/AMPA receptors with 6-cyano-7-nitroquinoxalene-2,3- dione. These findings demonstrate that the isolated mouse spinal cord can produce a variety of coordinated activities, including locomotor-like activity. The ability to study these behaviors under a variety of different conditions offers promise for future studies of rhythmogenic mechanisms in this preparation.