In vivo, competitive blockade of N-methyl-d-aspartate receptors induces rapid changes in filamentous actin and drebrin A distributions within dendritic spines of adult rat cortex

S. Fujisawa, T. Shirao, Chiye Aoki

Research output: Contribution to journalArticle

Abstract

In vitro studies have demonstrated that prolonged N-methyl-d-aspartate receptor (NMDAR) blockade triggers a homeostatic up-regulation of NMDARs at synapses. Such upregulation can also be seen within 30 min in vivo in adult rats, implicating trafficking of reserve pools of NMDARs. Here, we evaluated the involvement of filamentous actin (F-actin), the major cytoskeletal component in spines, in this rapid in vivo homeostatic response, using biotinylated phalloidin as its probe. We also immuno-labeled spines for drebrin A, an F-actin-binding protein found at excitatory synapses and with a proposed role of modulating F-actin's cross-linking with one another and interactions with NMDARs. Quantitative 2-D analysis of ultrastructural images revealed that NMDAR blockade increased filamentous actin labeling per spine by 62.5% (P<0.005). The proportion of dendritic spines immuno-labeled for drebrin A also increased significantly, from 67.5% to 85% following NMDAR blockade (P<0.001), especially among larger spines. The frequency distributions of spine widths and postsynaptic density lengths were not affected by the d-(+)-2-amino-5-phosphonopentanoic acid (d-APV) treatment. However, the average postsynaptic density length was reduced by 25 nm among the fewer, drebrin A immuno-negative spines, indicating that drebrin A confers stability to synapse size. We propose that, in a homeostatic in vivo response, increases of drebrin A and F-actin within spines can enhance NMDAR trafficking by reducing cytoskeletal rigidity within the spine cytoplasm without changing the overt morphology of axo-spinous synapses. Alternatively or in addition, the cytoskeletal redistribution within spine cytoplasm may be triggered by the d-APV-induced, homeostatic up-regulation of NMDAR.

Original languageEnglish (US)
Pages (from-to)1177-1187
Number of pages11
JournalNeuroscience
Volume140
Issue number4
DOIs
StatePublished - 2006

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Dendritic Spines
Actins
Spine
2-Amino-5-phosphonovalerate
Synapses
Post-Synaptic Density
Up-Regulation
Cytoplasm
aspartic acid receptor
drebrins
Phalloidine
Microfilament Proteins

Keywords

  • activity-dependent
  • drebrin
  • electron-microscopy
  • F-actin
  • immunocytochemistry
  • trafficking

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

@article{fd58f65e68e24eddaab1f3f66996bbd9,
title = "In vivo, competitive blockade of N-methyl-d-aspartate receptors induces rapid changes in filamentous actin and drebrin A distributions within dendritic spines of adult rat cortex",
abstract = "In vitro studies have demonstrated that prolonged N-methyl-d-aspartate receptor (NMDAR) blockade triggers a homeostatic up-regulation of NMDARs at synapses. Such upregulation can also be seen within 30 min in vivo in adult rats, implicating trafficking of reserve pools of NMDARs. Here, we evaluated the involvement of filamentous actin (F-actin), the major cytoskeletal component in spines, in this rapid in vivo homeostatic response, using biotinylated phalloidin as its probe. We also immuno-labeled spines for drebrin A, an F-actin-binding protein found at excitatory synapses and with a proposed role of modulating F-actin's cross-linking with one another and interactions with NMDARs. Quantitative 2-D analysis of ultrastructural images revealed that NMDAR blockade increased filamentous actin labeling per spine by 62.5{\%} (P<0.005). The proportion of dendritic spines immuno-labeled for drebrin A also increased significantly, from 67.5{\%} to 85{\%} following NMDAR blockade (P<0.001), especially among larger spines. The frequency distributions of spine widths and postsynaptic density lengths were not affected by the d-(+)-2-amino-5-phosphonopentanoic acid (d-APV) treatment. However, the average postsynaptic density length was reduced by 25 nm among the fewer, drebrin A immuno-negative spines, indicating that drebrin A confers stability to synapse size. We propose that, in a homeostatic in vivo response, increases of drebrin A and F-actin within spines can enhance NMDAR trafficking by reducing cytoskeletal rigidity within the spine cytoplasm without changing the overt morphology of axo-spinous synapses. Alternatively or in addition, the cytoskeletal redistribution within spine cytoplasm may be triggered by the d-APV-induced, homeostatic up-regulation of NMDAR.",
keywords = "activity-dependent, drebrin, electron-microscopy, F-actin, immunocytochemistry, trafficking",
author = "S. Fujisawa and T. Shirao and Chiye Aoki",
year = "2006",
doi = "10.1016/j.neuroscience.2006.03.009",
language = "English (US)",
volume = "140",
pages = "1177--1187",
journal = "Neuroscience",
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T1 - In vivo, competitive blockade of N-methyl-d-aspartate receptors induces rapid changes in filamentous actin and drebrin A distributions within dendritic spines of adult rat cortex

AU - Fujisawa, S.

AU - Shirao, T.

AU - Aoki, Chiye

PY - 2006

Y1 - 2006

N2 - In vitro studies have demonstrated that prolonged N-methyl-d-aspartate receptor (NMDAR) blockade triggers a homeostatic up-regulation of NMDARs at synapses. Such upregulation can also be seen within 30 min in vivo in adult rats, implicating trafficking of reserve pools of NMDARs. Here, we evaluated the involvement of filamentous actin (F-actin), the major cytoskeletal component in spines, in this rapid in vivo homeostatic response, using biotinylated phalloidin as its probe. We also immuno-labeled spines for drebrin A, an F-actin-binding protein found at excitatory synapses and with a proposed role of modulating F-actin's cross-linking with one another and interactions with NMDARs. Quantitative 2-D analysis of ultrastructural images revealed that NMDAR blockade increased filamentous actin labeling per spine by 62.5% (P<0.005). The proportion of dendritic spines immuno-labeled for drebrin A also increased significantly, from 67.5% to 85% following NMDAR blockade (P<0.001), especially among larger spines. The frequency distributions of spine widths and postsynaptic density lengths were not affected by the d-(+)-2-amino-5-phosphonopentanoic acid (d-APV) treatment. However, the average postsynaptic density length was reduced by 25 nm among the fewer, drebrin A immuno-negative spines, indicating that drebrin A confers stability to synapse size. We propose that, in a homeostatic in vivo response, increases of drebrin A and F-actin within spines can enhance NMDAR trafficking by reducing cytoskeletal rigidity within the spine cytoplasm without changing the overt morphology of axo-spinous synapses. Alternatively or in addition, the cytoskeletal redistribution within spine cytoplasm may be triggered by the d-APV-induced, homeostatic up-regulation of NMDAR.

AB - In vitro studies have demonstrated that prolonged N-methyl-d-aspartate receptor (NMDAR) blockade triggers a homeostatic up-regulation of NMDARs at synapses. Such upregulation can also be seen within 30 min in vivo in adult rats, implicating trafficking of reserve pools of NMDARs. Here, we evaluated the involvement of filamentous actin (F-actin), the major cytoskeletal component in spines, in this rapid in vivo homeostatic response, using biotinylated phalloidin as its probe. We also immuno-labeled spines for drebrin A, an F-actin-binding protein found at excitatory synapses and with a proposed role of modulating F-actin's cross-linking with one another and interactions with NMDARs. Quantitative 2-D analysis of ultrastructural images revealed that NMDAR blockade increased filamentous actin labeling per spine by 62.5% (P<0.005). The proportion of dendritic spines immuno-labeled for drebrin A also increased significantly, from 67.5% to 85% following NMDAR blockade (P<0.001), especially among larger spines. The frequency distributions of spine widths and postsynaptic density lengths were not affected by the d-(+)-2-amino-5-phosphonopentanoic acid (d-APV) treatment. However, the average postsynaptic density length was reduced by 25 nm among the fewer, drebrin A immuno-negative spines, indicating that drebrin A confers stability to synapse size. We propose that, in a homeostatic in vivo response, increases of drebrin A and F-actin within spines can enhance NMDAR trafficking by reducing cytoskeletal rigidity within the spine cytoplasm without changing the overt morphology of axo-spinous synapses. Alternatively or in addition, the cytoskeletal redistribution within spine cytoplasm may be triggered by the d-APV-induced, homeostatic up-regulation of NMDAR.

KW - activity-dependent

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KW - electron-microscopy

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KW - immunocytochemistry

KW - trafficking

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U2 - 10.1016/j.neuroscience.2006.03.009

DO - 10.1016/j.neuroscience.2006.03.009

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JO - Neuroscience

JF - Neuroscience

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