Physiological studies on the development of neuronal mechanisms generating locomotion in the rat spinal cord

采用离体大鼠腰椎-后肢制剂研究了n -甲基- d， l-天冬氨酸（NMA）对新生大鼠运动能力产生的影响。记录两侧踝关节屈肌和伸肌的肌电图活动。浴用NMA （10-30 <micrn>M）引起屈肌和伸肌之间的交替节律性活动。每块肌肉节律性活动的频率取决于NMA剂量。在低浓度NMA下，伸肌的平均爆发持续时间明显长于屈肌。随着NMA剂量的增加，与屈肌相比，伸肌的平均爆发时间明显缩短。在上述浓度范围内，两后肢相应肌肉的活动总是交替发生。这种肌肉活动模式不受背根横断的影响。nma诱导的节律性活动在脊髓中矢状分裂后也被观察到。然而，节律性活动的频率明显降低，每块肌肉的平均爆发时间比劈裂前长得多。结果表明，NMA激活的中枢节律发生器存在于腰椎两侧。节律性运动活动的发展也用离体大鼠胎儿腰椎脊髓制剂进行了研究。用NMA溶液诱发节律性运动活动，并通过腰椎两侧的前根记录。结果发现，在E15.5及之后，浴用NMA可引起腹侧根的节律性活动。节律性活动的平均频率随着年龄的增长而增加。在脊髓中矢状分裂后，节律性活动也在所有阶段被唤起，这表明脊髓的每一侧甚至在胎儿阶段就有产生节律的神经元回路。两侧腹根节律性活动的相位关系在E15.5和E16.5时为同步，在E17.5时为独立，在@18.5-20.5时为交替。在E17.5。士的宁的加入使两侧的独立节律活动变为同步模式，而在早期阶段没有效果。这表明在这一阶段，某些抑制通路在神经元回路两侧的功能偶联中起着重要作用。少

Effects of N-methyl-D,L-aspartate (NMA) on the generation of locomortor activity were studied using isolated lumbar spinal cord-hind limb preparations in new-born rats.Electromyographic activities were recorded from the ankle flexor and extensor muscles of both sides. Bath-applied NMA (10-30 <micrn>M) evoked alternating rhythmic activity between the flexors and extensors. The frequency of the rhythmic activity in each muscle depended on the NMA dose. The mean burst duration in extensors was considerably longer than that in flexors at low concentrations of NMA. When the NMA dose was increased, the mean burst duration in extensors markedly decreased, compared with that in flexors. The activity in the corresponding muscles of the two hind limbs always occurred alternatingly within the concentration ranged described above. This pattern of muscle activity was not affected by the dorsal root transection. The NMA-induced rhythmic activity was also observed after the spinal cord was split mid- … More sagittally. However, the frequency of the rhythmic activity was significantly lower and the mean burst duration in each muscle much longer than those before splitting. It was concluded that central rhythm generators, activated by NMA, exist in both sides of the lumbar spinal cord.The development of rhythmic motor activity was also studied using isolated lumbar spinal cord preparations of rat fetuses. Rhythmic motor activity was evoked by bath application of NMA and recorded through the ventral roots on both sides of the lumbar spinal cord. It was found that rhythmic activity in the ventral roots was elicited by bath-applied NMA at and after E15.5. The mean frequency of the rhythmic activity increased with age. The rhythythmic activity was also evoked at all stages after splitting the spinal cord midsagitally, indicating that each side of the spinal cord has neuronal circuits for rhythm generation even at the fetal stage.the phase relationship of the rhythmic activities between the two sides of the ventral roots was synchrous st E15.5 and E16.5, independent at E17.5 and alternating at @18.5-20.5. At E17.5. the addition of strvchnine changed the independent rhythimic activities between the two sides to a synchrounous pattern, while at earlier stages it had no effect. This suggets that some inhibitory pathways to play an inportant role of functional couplimg between the two sides of neuronal circuits at this stage. Less