Presynaptic Development at L4 to L2/3 Excitatory Synapses Follows Different Time Courses in Visual and Somatosensory Cortex
Presynaptic Development at L4 to L2/3 Excitatory Synapses Follows Different Time Courses in Visual and Somatosensory Cortex
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DOI：
10.1523/jneurosci.2544-10.2010
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发表时间：
2010-09-22
影响因子：
5.3
通讯作者：
Fox, Kevin
中科院分区：
文献类型：
--
作者：
Cheetham, Claire E. J.;Fox, Kevin
视觉和体感觉皮层在发育和成年期间表现出深刻的经验依赖可塑性，是探索可塑性的突触和分子机制的常见模型系统。但是，由于缺乏关于这两个地区相对发展速度的准确资料，对这两个地区的比较可能会受到干扰。本研究采用急性脑切片全细胞记录的方法研究小鼠脑桶皮层和视皮层突触发育。我们发现短期可塑性（STP）从出生后12天的强烈抑郁转变为成熟皮层的较弱抑郁和易化。然而，相对于桶状皮层，视觉皮层(L) 4层至L2/3层兴奋性突触的突触前成熟延迟了2周。这种发育迟缓是通路特异性的；桶状皮层和视觉皮层L2/3到L2/3突触成熟的时间尺度相似。配对脉冲比大于1的发育性增加反映在突触前释放概率的发育性降低上。因此，P28时，桶状皮层L4 ~ L2/3兴奋性突触的释放概率较低，短期易化程度高于视觉皮层。突触后机制不能解释STP在视觉皮层的延迟成熟。这些发现表明，突触发育在视觉皮层的L4至L2/3通路中被延迟，并强调在比较不同皮质区域的可塑性机制时，需要考虑突触特性在发育过程中发生的变化。
Visual and somatosensory cortices exhibit profound experience-dependent plasticity during development and adulthood and are common model systems for probing the synaptic and molecular mechanisms of plasticity. However, comparisons between the two areas may be confounded by a lack of accurate information on their relative rates of development. In this study, we used whole-cell recording in acute brain slices to study synaptic development in mouse barrel and visual cortex. We found that short-term plasticity (STP) switched from strong depression at postnatal day (P) 12 to weaker depression and facilitation in mature cortex. However, presynaptic maturation was delayed by similar to 2 weeks at layer (L) 4 to L2/3 excitatory synapses in visual cortex relative to barrel cortex. This developmental delay was pathway-specific; maturation of L2/3 to L2/3 synapses occurred over similar timescales in barrel and visual cortex. The developmental increase in the paired-pulse ratio to values greater than unity was mirrored by a developmental decrease in presynaptic release probability. Therefore, L4 to L2/3 excitatory synapses had lower release probabilities and showed greater short-term facilitation in barrel cortex than in visual cortex at P28. Postsynaptic mechanisms could not account for the delayed maturation of STP in visual cortex. These findings indicate that synaptic development is delayed in the L4 to L2/3 pathway in visual cortex, and emphasize the need to take into account the changes in synaptic properties that occur during development when comparing plasticity mechanisms in different cortical areas.