A competition-based mechanism mediates developmental refinement of tectal neuron receptive fields.
A competition-based mechanism mediates developmental refinement of tectal neuron receptive fields.
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DOI：
10.1523/jneurosci.2372-12.2012
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发表时间：
2012-11-21
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通讯作者：
Aizenman CD
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作者：
Dong W;Aizenman CD
神经活动在大脑视觉回路的发育和成熟中起着重要作用。活动可以是有益的，通过直接介导的形成和消除特定的突触接触，通过竞争为基础的机制，在细化视觉投影。或者，活动可以是允许的-调节因素的产生，为回路的完善创造有利的环境。在这里，我们使用非洲爪蟾蝌蚪视觉系统，以测试是否活动是有益的或许可的视网膜顶盖回路的形成发展。在体内尖峰输出抑制在一个小组的顶盖神经元，从发展阶段44-46，过表达摇床样爪蟾Kv1.1钾通道，使用电穿孔。然后饲养蝌蚪直到第49阶段，这是视网膜顶盖图发生显著细化的时间段。Kv1.1表达的神经元有显着降低尖峰输出响应电流注入和视觉刺激，与未转染的对照相比，尖峰发生在一个更有限的时间间隔。我们发现，Kv1.1表达神经元具有更大的视觉感受野，感受野锐度下降和更持久的反复兴奋比对照神经元，所有这些都是未成熟神经元的特征。然而，转染细胞具有正常的自发兴奋性突触电流和树突状动脉。这些结果表明，顶盖神经元的锋电位输出在其感受野特性的发育和局部回路的完善中起着重要的指导作用。然而，其他活动依赖的过程，如突触发生和树突生长，保持不受影响，由于其他正常的网络活动所创造的许可环境。
Neural activity plays an important role in development and maturation of visual circuits in the brain. Activity can be instructive in refining visual projections by directly mediating formation and elimination of specific synaptic contacts through competition-based mechanisms. Alternatively, activity could be permissive – regulating production of factors which create a favorable environment for circuit refinement. Here we used the Xenopus laevis tadpole visual system to test whether activity is instructive or permissive for shaping development of the retinotectal circuit. In vivo spike output was dampened in a small subgroup of tectal neurons, starting from developmental stages 44–46, by overexpressing Shaker-like Xenopus Kv1.1 potassium channels using electroporation. Tadpoles were then reared until stage 49, a time period when significant refinement of the retinotectal map occurs. Kv1.1 expressing neurons had significantly decreased spike output in response to both current injection and visual stimuli, compared to untransfected controls, with spiking occurring during a more limited time interval. We found that Kv1.1 expressing neurons had larger visual receptive fields, decreased receptive field sharpness and more persistent recurrent excitation than control neurons, all of which are characteristics of immature neurons. Transfected cells, however had normal spontaneous excitatory synaptic currents and dendritic arbors. These results suggest that spike output of a tectal neuron plays an important instructive role in development of its receptive field properties and refinement of local circuits. However, other activity dependent processes, such as synaptogenesis and dendritic growth, remain unaffected due to the permissive environment created by otherwise normal network activity.