Roerig B, Feller M B
Department of Anatomy and Neurobiology, School of Medicine, University of Maryland, Baltimore, MD, USA.
Brain Res Brain Res Rev. 2000 Apr;32(1):86-114. doi: 10.1016/s0165-0173(99)00069-7.
A growing body of evidence suggests that highly correlated, spontaneous neural activity plays an important role in shaping connections in the developing nervous system prior to the maturation of sensory afferents. In this article we discuss the mechanisms involved in the generation and the regulation of spontaneous activity patterns in the developing retina and the developing neocortex. Spontaneous activity in the developing retina propagates across the ganglion cell layer as waves of action potentials and drives rhythmic increases in intracellular calcium in retinal neurons. Retinal waves are mediated by a combination of chemical synaptic transmission and gap junctions, and the circuitry responsible for generating retinal waves changes with age and between species. In the developing cortex, spontaneous calcium elevations propagate across clusters of cortical neurons called domains. Cortical domains are generated by a regenerative mechanism involving second messenger diffusion through gap junctions and subsequent calcium release from internal stores. The neocortical gap junction system is regulated by glutamate-triggered second messenger systems as well as neuromodulatory transmitters, suggesting extensive interactions between synaptic transmission and information flow through gap junctions. The interaction between gap junctions and chemical synaptic transmission observed in these developing networks represent a powerful mechanism by which activity across large groups of neurons can be correlated.
越来越多的证据表明，在感觉传入成熟之前，高度相关的自发神经活动在发育中的神经系统连接形成中起着重要作用。在本文中，我们讨论了发育中的视网膜和发育中的新皮质中自发活动模式的产生和调节机制。发育中的视网膜中的自发活动以动作电位波的形式在神经节细胞层中传播，并驱动视网膜神经元细胞内钙的节律性增加。视网膜波由化学突触传递和缝隙连接共同介导，负责产生视网膜波的电路随年龄和物种而异。在发育中的皮质中，自发的钙升高在称为区域的皮质神经元簇中传播。皮质区域由一种再生机制产生，该机制涉及通过缝隙连接的第二信使扩散以及随后从内部储存中释放钙。新皮质缝隙连接系统受谷氨酸触发的第二信使系统以及神经调节递质的调节，这表明突触传递和通过缝隙连接的信息流之间存在广泛的相互作用。在这些发育中的网络中观察到的缝隙连接和化学突触传递之间的相互作用代表了一种强大的机制，通过该机制可以使大量神经元之间的活动相关联。
