Loading…

Factors regulating AMPA-type glutamate receptor subunit changes induced by sciatic nerve injury in rats

Excitatory glutamatergic neurotransmission at Ia afferent‐motoneuron synapses is enhanced shortly after physically severing or blocking impulse propagation of the afferent and/or motoneuron axons. We considered the possibility that these synaptic changes occur because of alterations in the number or...

Full description

Saved in:
Bibliographic Details
Published in:Journal of comparative neurology (1911) 2000-10, Vol.426 (2), p.229-242
Main Authors: Alvarez, Francisco J., Fyffe, Robert E.W., Dewey, Dianne E., Haftel, Valerie K., Cope, Timothy C.
Format: Article
Language:English
Subjects:
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Excitatory glutamatergic neurotransmission at Ia afferent‐motoneuron synapses is enhanced shortly after physically severing or blocking impulse propagation of the afferent and/or motoneuron axons. We considered the possibility that these synaptic changes occur because of alterations in the number or properties of motoneuron α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionate (AMPA) receptors. Therefore, we quantitatively analyzed glutamate receptor (GluR)1, GluR2/3, and GluR4 AMPA subunit immunoreactivity (ir) in motoneurons 3, 7, or 14 days after axotomy or continuous tetrodotoxin (TTX) block of the sciatic nerve. GluR1‐ir remained low in experimental and control motoneurons with either treatment and at any date. However, there was a large reduction of GluR2/3‐ir (peak at 7 days >60% reduced) and a smaller, but statistically significant, reduction of GluR4‐ir (around 10% reduction at days 3, 7, and 14) in axotomized motoneurons. TTX sciatic blockade did not affect AMPA subunit immunostainings. Axonal injury or interruption of the trophic interaction between muscle and spinal cord, but not activity disruption, appears therefore more likely responsible for altering AMPA subunit immunoreactivity in motoneurons. These findings also suggest that synaptic plasticity induced by axotomy or TTX block, although similar in the first week, could be related to different mechanisms. The effects of axotomy or TTX block on motoneuron expression of the metabotropic glutamate receptor mGluR1a were also studied. mGluR1a‐ir was also strongly decreased after axotomy but not after TTX treatment. The time course of the known stripping of synapses from the cell somas of axotomized motoneurons was studied by using synaptophysin antibodies and compared with AMPA and mGluR1a receptor changes. Coverage by synaptophysin‐ir boutons was only clearly decreased 14 days post axotomy and not at shorter intervals or after TTX block. J. Comp. Neurol. 426:229–242, 2000. © 2000 Wiley‐Liss, Inc.
ISSN:0021-9967
1096-9861
DOI:10.1002/1096-9861(20001016)426:2<229::AID-CNE5>3.0.CO;2-W