Activity-dependent plasticity in the olfactory intrabulbar map
Activity-dependent plasticity in the olfactory intrabulbar map
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DOI：
10.1523/jneurosci.2805-06.2006
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发表时间：
2006-11-01
影响因子：
5.3
通讯作者：
Belluscio, Leonardo
中科院分区：
文献类型：
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作者：
Marks, Carolyn A.;Cheng, Kai;Belluscio, Leonardo
在哺乳动物中，每个嗅球包含两个镜像对称的肾小球地图。每个球内的等功能肾小球通过一组相互的球内投射（IBP）特异性地连接，以形成球内图。我们将神经示踪剂注射到球的一侧的肾小球层，并检查了在另一侧产生的投影。在成年小鼠中，突起簇的大小与注射区域的大小成正比。使用该比率作为IBP成熟度的测量，我们发现在1周龄时未成熟的5：1投射与注射比率逐渐细化到7周龄时的成熟的1：1。此外，尽管消除了气味诱导的活动，但肾小球地图仍能够形成，而球内地图显示出其精确形成的明确的活动依赖性。在这里，我们表明，通过实验与鼻孔闭塞和嗅觉缺失的小鼠，气味诱导的活动是不需要建立IBP，但投影细化是至关重要的。相比之下，通过在地图开发过程中暴露于不同的气味剂而增加的肾小球激活可以加速与激活的肾小球相关的预测的细化。这些发现说明了气味诱导的活动在塑造灯泡内部电路中的明确作用。有趣的是，活动剥夺可以改变组织的发展和成熟的地图到相同的程度，表明球内地图的可塑性保持到成年期，没有明显的关键时期。
In mammals, each olfactory bulb contains two mirror-symmetric glomerular maps. Isofunctional glomeruli within each bulb are specifically linked through a set of reciprocal intrabulbar projections (IBPs) to form an intrabulbar map. We injected neural tracers into the glomerular layer on one side of the bulb and examined the resulting projection on the opposite side. In adult mice, the size of the projection tuft is directly proportional to the size of the injected region. Using this ratio as a measure of IBP maturity, we find an immature 5: 1 projection to injection ratio at 1 week of age that gradually refines to a mature 1: 1 by 7 weeks. Moreover, whereas the glomerular map is able to form despite the elimination of odorant-induced activity, the intrabulbar map shows clear activity dependence for its precise formation. Here we show through experiments with both naris-occluded and anosmic mice that odorant-induced activity is not required to establish IBPs but is crucial for projection refinement. In contrast, increased glomerular activation through exposure to distinct odorants during map development can accelerate the refinement of projections associated with the activated glomeruli. These findings illustrate a clear role for odorant-induced activity in shaping the internal circuitry of the bulb. Interestingly, activity deprivation can alter the organization of both the developing and the mature map to the same degree, demonstrating that intrabulbar map plasticity is maintained into adulthood with no discernible critical period.