Differentiation of Central Pattern Generators in the rat.

参与运动的节律性运动活动通常被认为是由脊髓内的神经元间网络产生的。取胎鼠脊髓标本，观察5-羟色胺诱导的运动节律的发育变化。从L2/L3和L5腹根记录到运动活动，分别代表屈肌和伸肌的活动。在E16.5研究中，沐浴应用5-羟色胺可引起所有前根同步的节律性爆发。在E18.5时，5-羟色胺诱发双侧交替的节律性爆发，而L2/L3前根的爆发与同侧L5前根的爆发同步。在E20.5时，5-羟色胺在L2/L3和L5腹根引起交替性节律性爆发。在士的宁存在的情况下，5-羟色胺诱发的节律性猝发在E18.5和E20.5的所有腹根中是同步的，这表明随着年龄的增长，节律性运动活动模式的改变是由于甘氨酸介导的抑制的发展。在早期(E14.5-E16.5)胎儿的准备中，我们观察到5-羟色胺诱发的节律性猝发，在相应的腹根的两侧是同步的。谷氨酸受体阻断剂犬尿酸不能阻断这些节律性爆发，但甘氨酸受体拮抗剂士的宁可以完全消除这种节律性爆发。甘氨酸在前根引起兴奋性反应的简单应用。这些结果表明，在发育过程中甘氨酸诱导的反应的功能变化在产生运动的神经元回路的分化中起着重要的作用。

The rhythmic motor activity involved in locomotion is generally considered to be generated by interneuronal networks within the spinal cord. Developmental changes in the 5-HT-induced locomotor rhythm were examined in isolated spinal cord preparations taken from fetal rats. Motor activity was recorded from L2/L3 and L5 ventral roots, representing activity in flexors and extensors, respectively. Bath application of 5-HT evoked rhythmic bursts that were synchronized in all ventral roots studied at E16.5. At E18.5, 5-HT evoked rhythmic bursts that alternated between the two sides, while the bursts in the L2/L3 ventral root were synchronous with those in the ipsilateral L5 ventral root. At E20.5, 5-HT evoked alternate rhythmic bursts in L2/L3 and L5 ventral roots. In the presence of strychnine, 5-HT induced rhythmic bursts that were synchronized in all ventral roots studied at E18.5 and E20.5, suggesting that the change in the pattern of rhythmic motor activity that occurs with age is due to the development of glycine-mediated inhibition.In preparations from fetuses at the earlier stages (E14.5 - E16.5), we observed 5-HT evoked rhythmic bursts , which were synchronized on the two sides in the corresponding ventral roots. These rhythmic bursts were not blocked by kynurenate, the glutamate receptor blocker, though it was completely abolished by strychnine, the glycine receptor antagonist. A brief application of glycine evoked excitatory responses in the ventral roots. It is concluded that glycine functions transiently as excitatory transmitters at these stages.These results suggest that functional change in glycine-induced responses during development plays an important role in differentiation of the neuronal circuits generating locomotion.