Abstract
Increases in cytosolic Ca2+ concentration ([Ca2+]i) mediated by NMDA-sensitive glutamate receptors (NMDARs) are important for synaptic plasticity. We studied a wide variety of dendritic spines on rat CA1 pyramidal neurons in acute hippocampal slices. Two-photon uncaging and Ca2+ imaging revealed that NMDAR-mediated currents increased with spine-head volume and that even the smallest spines contained a significant number of NMDARs. The fate of Ca2+ that entered spine heads through NMDARs was governed by the shape (length and radius) of the spine neck. Larger spines had necks that permitted greater efflux of Ca2+ into the dendritic shaft, whereas smaller spines manifested a larger increase in [Ca2+]i within the spine compartment as a result of a smaller Ca2+ flux through the neck. Spine-neck geometry is thus an important determinant of spine Ca2+ signaling, allowing small spines to be the preferential sites for isolated induction of long-term potentiation.
Publication types
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Comparative Study
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Animals, Newborn
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Calcium / metabolism
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Calcium Signaling / drug effects
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Calcium Signaling / physiology*
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Dendritic Spines / drug effects
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Dendritic Spines / metabolism*
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Diagnostic Imaging / methods
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Dose-Response Relationship, Radiation
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Glutamates / metabolism
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Glutamates / pharmacology
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Hippocampus / cytology*
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In Vitro Techniques
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Indoles / metabolism
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Indoles / pharmacology
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Lasers
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Membrane Potentials / radiation effects
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Models, Neurological
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N-Methylaspartate / pharmacology
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Patch-Clamp Techniques / methods
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Pyramidal Cells / cytology*
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Pyramidal Cells / drug effects
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Pyramidal Cells / physiology*
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Rats
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Rats, Sprague-Dawley
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Receptors, N-Methyl-D-Aspartate / agonists
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Receptors, N-Methyl-D-Aspartate / analysis
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Receptors, N-Methyl-D-Aspartate / metabolism*
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Synaptic Transmission / radiation effects
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Valine / analogs & derivatives*
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Valine / pharmacology
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alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology
Substances
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4-methoxy-7-nitroindolinyl-glutamate
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Glutamates
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Indoles
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Receptors, N-Methyl-D-Aspartate
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N-Methylaspartate
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2-amino-5-phosphopentanoic acid
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alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
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Valine
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Calcium