Neuron
Volume 49, Issue 6, 16 March 2006, Pages 861-875
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Article
Cell Type-Specific Structural Plasticity of Axonal Branches and Boutons in the Adult Neocortex

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Summary

We imaged axons in layer (L) 1 of the mouse barrel cortex in vivo. Axons from thalamus and L2/3/5, or L6 pyramidal cells were identified based on their distinct morphologies. Their branching patterns and sizes were stable over times of months. However, axonal branches and boutons displayed cell type-specific rearrangements. Structural plasticity in thalamocortical afferents was mostly due to elongation and retraction of branches (range, 1–150 μm over 4 days; ∼5% of total axonal length), while the majority of boutons persisted for up to 9 months (persistence over 1 month ∼85%). In contrast, L6 axon terminaux boutons were highly plastic (persistence over 1 month ∼40 %), and other intracortical axon boutons showed intermediate levels of plasticity. Retrospective electron microscopy revealed that new boutons make synapses. Our data suggest that structural plasticity of axonal branches and boutons contributes to the remodeling of specific functional circuits.

MOLNEURO

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