Abstract
The rapid motility of axonal filopodia and dendritic spines is prevalent throughout the developing CNS, although the function of this motility remains controversial. Using two-photon microscopy, we imaged hippocampal mossy fiber axons in slice cultures and discovered that filopodial extensions are highly motile. Axonal filopodial motility is actin based and is downregulated with development, although it remains in mature cultures. This motility is correlated with free extracellular space yet is inversely correlated with contact with postsynaptic targets, indicating a potential role in synaptogenesis. Filopodial motility is differentially regulated by kainate receptors: synaptic stimulation of kainate receptors enhances motility in younger slices, but it inhibits it in mature slices. We propose that neuronal activity controls filopodial motility in a developmentally regulated manner, in order to establish synaptic contacts in a two-step process. A two-step model of synaptogenesis can also explain the opposite effects of neuronal activity on the motility of dendritic protrusions.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actin Cytoskeleton / metabolism
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Animals
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Animals, Newborn
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Cell Communication / drug effects
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Cell Communication / physiology
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Cell Differentiation / drug effects
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Cell Differentiation / physiology*
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Cell Movement / drug effects
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Cell Movement / physiology*
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Electric Stimulation
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Excitatory Amino Acid Agonists / pharmacology
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Extracellular Space / metabolism
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Glutamic Acid / metabolism*
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Glutamic Acid / pharmacology
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Growth Cones / metabolism*
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Growth Cones / ultrastructure
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Mice
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Microscopy, Electron
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Mossy Fibers, Hippocampal / growth & development*
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Mossy Fibers, Hippocampal / metabolism
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Mossy Fibers, Hippocampal / ultrastructure
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Organ Culture Techniques
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Pseudopodia / metabolism*
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Pseudopodia / ultrastructure
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Receptors, Kainic Acid / antagonists & inhibitors
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Receptors, Kainic Acid / metabolism*
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Synaptic Membranes / drug effects
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Synaptic Membranes / metabolism
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
Substances
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Excitatory Amino Acid Agonists
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Receptors, Kainic Acid
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Glutamic Acid