Sodium dynamics in pyramidal neuron dendritic spines : synaptically evoked entry predominantly through AMPA receptors and removal by diffusion
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Dendritic spines are key elements underlying synaptic integration and cellular plasticity, but many features of these important structures are not known or are controversial. We examined these properties using newly developed simultaneous sodium and calcium imaging with single-spine resolution in pyramidal neurons in rat hippocampal slices from either sex. Indicators for both ions were loaded through the somatic patch pipette, which also recorded electrical responses. Fluorescence changes were detected with a high-speed, low-noise CCD camera. Following subthreshold electrical stimulation, postsynaptic sodium entry is almost entirely through AMPA receptors with little contribution from entry through NMDA receptors or voltage-gated sodium channels. Sodium removal from the spine head is through rapid diffusion out to the dendrite through the spine neck with a half-removal time of ∼16 ms, which suggests the neck has low resistance. Peak [Na+]i changes during single EPSPs are ∼5 mm. Stronger electrical stimulation evoked small plateau potentials that had significant longer-lasting localized [Na+]i increases mediated through NMDA receptors.
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience 37 (2017): 9964-9976, doi:10.1523/JNEUROSCI.1758-17.2017.
Suggested CitationJournal of Neuroscience 37 (2017): 9964-9976
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