The role of electrical activity in the development of sensorimotor networks in mammals

神经活动在神经系统的发育中起着重要作用，但涉及的机制在很大程度上仍是未知的。这种活动有两种不同的形式：一种是神经网络在发育过程中产生的“自发”活动，另一种是由神经网络的外在刺激产生的“经验依赖”活动。自发活动是一种非常早期的现象，与神经结构发育的几个阶段（轴突生长、突触发生）有关。自发活动的早熟表达解释了在哺乳动物中，它主要在发育较晚的结构（视网膜，皮层）中进行研究。由于实验模型的错误，早期发育的结构，如脊髓运动网络，在很大程度上被忽略了。我们使用了一种原始的哺乳动物模型，即家负鼠，允许通过不同的方法（解剖学、生理学、药理学和行为学）对自发活动的机制进行实验研究。利用体外脑干脊髓制备，我们发现自发性活动在出生后胚胎的脊髓中表达，并开始研究其产生的机制。我们将继续在不同年龄研究这种活性的生理和药理学基础。我们还将描述脊髓运动网络的解剖和生理特征模式。通过药理学手段对自发活动的任何干扰都应引起这些模式的改变，从而可以推断这种活动在网络成熟中的作用。我们还将研究诱发活动对这些模式的影响，使用三叉神经系统作为模型，比较每种形式的神经活动的各自影响。该研究项目为更深入地研究自发活动的生理机制奠定了必要的基础，这些机制在很大程度上是未知的，但在神经系统的成熟中起着重要作用。

Neural activity plays a role in the development of the nervous system but the mechanisms involved are still largely unknown. Two different forms of this activity can be distinguished: "spontaneous" activity that is intrinsically generated in neural networks during development, and "experience dependent" activity that is generated by extrinsic stimulation of the networks. Spontaneous activity is a very early phenomenon which is associated with several phases of the development of neural structures (axon growth, synaptogenesis). The precocious expression of spontaneous activity explains that in mammals it is mostly studied in structures that develop lately (retina, cortex). Structures that develop very early, such as the spinal motor networks, were largely ignored by fault of an experimental model. We use an original mammalian model, the opossum Monodelphis domestica, allowing experimental studies of the mechanisms underlying spontaneous activity by different approaches (anatomical, physiological, pharmacological and behavioral). Using in vitro brainstem spinal-cord preparations, we have showed that spontaneous activity is expressed in the spinal cord of postnatal embryos and started to study the mechanisms underlying its generation. We will continue to investigate the physiological and pharmacological basis of this activity at different ages. We will also describe the spinal motor networks anatomical and physiological characteristic patterns. Any disturbance of the spontaneous activity by pharmacological means should induce modifications of these patterns, allowing inference to the role of this activity in the maturation of the networks. We will also study the effects of evoked activity on these patterns, using the trigeminal systems as a model, to compare the respective impact of each form of nervous activity. This research program is a necessary groundwork for a more thorough study of the physiological mechanisms underlying spontaneous activity, mechanisms which are largely unknown but which play an essential part in the maturation of the nervous system.