Yvert Blaise, Branchereau Pascal, Meyrand Pierre
Laboratoire de Neurobiologie des Réseaux, Unité Mixte de Recherche 5816, Centre National de la Recherche Scientifique and Université Bordeaux 1, 33405 Talence Cedex, France.
J Neurophysiol. 2004 May;91(5):2101-9. doi: 10.1152/jn.01095.2003. Epub 2004 Jan 14.
Spontaneous rhythmic activity is a ubiquitous phenomenon in developing neural networks and is assumed to play an important role in the elaboration of mature circuitry. Here we describe the day-by-day evolution of spontaneous activity in the embryonic mouse spinal cord and show that, at a specific developmental stage, 2 distinct rhythms coexist. On embryonic days E12.5 and E13.5, we observed a single type of regularly recurring short spike-episodes synchronized across cervical, thoracic, and lumbar levels. By E14.5, in addition to this motor rhythm, another type of spontaneous synchronous activity appeared, characterized by much longer lasting episodes separated by longer time intervals. On E15.5, these long episodes disappeared. Short episodes were less numerous and more irregular except at the cervical level where a rhythm was occasionally observed. By E16.5, this cervical rhythm became more robust, whereas the lumbar level fell almost silent. Surprisingly, at E17.5, spontaneous activity resumed at caudal levels, now characterized by numerous erratic short episodes. A striking ontogenetic feature of spontaneous activity was the occurrence of long episodes only at E14.5. Although concomitant at all levels of the spinal cord, long episodes displayed different patterns along the spinal cord, with tonic firing at the thoracic level and rhythmic discharge with occasional sequences of left/right alternation at the lumbar level. Thus at E14.5, the originally synchronized network has started to segregate into more specialized subnetworks. In conclusion, this work suggests that ongoing spontaneous rhythms do not follow a smooth evolution during maturation, but rather undergo profound changes at very specific stages.
自发节律性活动是发育中的神经网络中普遍存在的现象，被认为在成熟神经回路的形成中起重要作用。在这里，我们描述了胚胎小鼠脊髓中自发活动的逐日演变，并表明在特定的发育阶段，两种不同的节律共存。在胚胎期第12.5天和13.5天，我们观察到一种单一类型的有规律重复的短脉冲发作，在颈段、胸段和腰段同步。到第14.5天，除了这种运动节律外，另一种自发同步活动出现了，其特征是持续时间长得多的发作，间隔时间也更长。在第15.5天，这些长发作消失了。短发作数量减少且更不规则，除了在颈段偶尔观察到一种节律。到第16.5天，这种颈段节律变得更强健，而腰段几乎沉默。令人惊讶的是，在第17.5天，尾部水平的自发活动恢复，现在以大量不规则的短发作特征。自发活动一个显著的个体发生特征是长发作仅在第14.5天出现。尽管在脊髓的所有水平都同时存在，但长发作在脊髓上显示出不同的模式，胸段为强直性放电，腰段为有节律的放电，偶尔有左右交替序列。因此，在第14.5天，最初同步的网络已开始分离成更专门的子网。总之，这项工作表明，正在进行的自发节律在成熟过程中并非平稳演变，而是在非常特定的阶段经历深刻变化。
