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Widespread expression of the AMPA receptor GluR2 subunit at glutamatergic synapses in the rat spinal cord and phosphorylation of GluR1 in response to noxious stimulation revealed with an antigen-unmasking method.

ABSTRACT: Glutamate, the principal excitatory neurotransmitter in the spinal cord, acts primarily through AMPA receptors. Although all four AMPA subunits are expressed by spinal neurons, we know little about their distribution at glutamatergic synapses. We used an antigen-unmasking technique to reveal the synaptic distribution of glutamate receptor (GluR) 1-4 subunits with confocal microscopy. After pepsin treatment, punctate staining was seen with antibodies against each subunit: GluR2-immunoreactive puncta were distributed throughout the gray matter, whereas GluR1-immunoreactive puncta were restricted to the dorsal horn and were most numerous in laminas I-II. Punctate staining for GluR3 and GluR4 was found in all laminas but was weak in superficial dorsal horn. Colocalization studies showed that GluR2 was present at virtually all (98%) puncta that were GluR1, GluR3, or GluR4 immunoreactive and that most (>90%) immunoreactive puncta in laminas IV, V, and IX showed GluR2, GluR3, and GluR4 immunoreactivity. Evidence that these puncta represented synaptic receptors was obtained with electron microscopy and by examining the association of GluR2- and GluR1-immunoreactive puncta with glutamatergic boutons (identified with vesicular glutamate transporters or markers for unmyelinated afferents). The great majority (96%) of these boutons were associated with GluR2-immunoreactive puncta. Our findings suggest that GluR2 is almost universally present at AMPA-containing synapses, whereas GluR1 is preferentially associated with primary afferent terminals. We also found a substantial, rapid increase in staining for synaptic GluR1 subunits phosphorylated on the S845 residue in the ipsilateral dorsal horn after peripheral noxious stimulation. This finding demonstrates plastic changes, presumably contributing to central sensitization, at the synaptic level.

SUBMITTER: Nagy GG

PROVIDER: S-EPMC6729210 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

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Widespread expression of the AMPA receptor GluR2 subunit at glutamatergic synapses in the rat spinal cord and phosphorylation of GluR1 in response to noxious stimulation revealed with an antigen-unmasking method.

Nagy Gergely G GG Al-Ayyan Muna M Andrew David D Fukaya Masahiro M Watanabe Masahiko M Todd Andrew J AJ

The Journal of neuroscience : the official journal of the Society for Neuroscience 20040601 25

Glutamate, the principal excitatory neurotransmitter in the spinal cord, acts primarily through AMPA receptors. Although all four AMPA subunits are expressed by spinal neurons, we know little about their distribution at glutamatergic synapses. We used an antigen-unmasking technique to reveal the synaptic distribution of glutamate receptor (GluR) 1-4 subunits with confocal microscopy. After pepsin treatment, punctate staining was seen with antibodies against each subunit: GluR2-immunoreactive pun ...[more]

PMID: 15215299

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Project description:Astrocytes, an abundant form of glia, are known to promote and modulate synaptic signaling between neurons. They also express ?7-containing nicotinic acetylcholine receptors (?7-nAChRs), but the functional relevance of these receptors is unknown. We show here that stimulation of ?7-nAChRs on astrocytes releases components that induce hippocampal neurons to acquire more ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors post-synaptically at glutamatergic synapses. The increase is specific in that no change is seen in synaptic NMDA receptor clusters or other markers for glutamatergic synapses, or in markers for GABAergic synapses. Moreover, the increases in AMPA receptors on the neuron surface are accompanied by increases in the frequency of spontaneous miniature synaptic currents mediated by the receptors and increases in the ratio of evoked synaptic currents mediated by AMPA versus NMDA receptors. This suggests that stimulating ?7-nAChRs on astrocytes can convert 'silent' glutamatergic synapses to functional status. Astrocyte-derived thrombospondin is necessary but not sufficient for the effect, while tumor necrosis factor-? is sufficient but not necessary. The results identify astrocyte ?7-nAChRs as a novel pathway through which nicotinic cholinergic signaling can promote the development of glutamatergic networks, recruiting AMPA receptors to post-synaptic sites and rendering the synapses more functional. We find that activation of nicotinic receptors on astrocytes releases a component that specifically recruits AMPA receptors to glutamatergic synapses. The recruitment appears to occur preferentially at what may be 'silent synapses', that is, synapses that have all the components required for glutamatergic transmission (including NMDA receptors) but lack sufficient AMPA receptors to generate a response. The results are unexpected and open up new possibilities for mechanisms underlying network formation and synaptic plasticity.

Dataset Information

Widespread expression of the AMPA receptor GluR2 subunit at glutamatergic synapses in the rat spinal cord and phosphorylation of GluR1 in response to noxious stimulation revealed with an antigen-unmasking method.

Publications

Widespread expression of the AMPA receptor GluR2 subunit at glutamatergic synapses in the rat spinal cord and phosphorylation of GluR1 in response to noxious stimulation revealed with an antigen-unmasking method.

Similar Datasets

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