Evidence for low GluR2 AMPA receptor subunit expression at synapses in the rat basolateral amygdala

Divina S. Gryder, Dora C. Castaneda, Michael A Rogawski

Research output: Contribution to journalArticle

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Abstract

Fast excitatory synaptic responses in basolateral amygdala (BLA) neurons are mainly mediated by ionotropic glutamate receptors of the a-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) subtype. AMPA receptors containing an edited GluR2 subunit are calcium impermeable, whereas those that lack this subunit are calcium permeable and also inwardly rectifying. Here, we sought to determine the extent to which synapses in the rat BLA have AMPA receptors with GluR2 subunits. We assessed GluR2 protein expression in the BLA by immunocytochemistry with a GluR2 subunit-specific antiserum at the light and electron microscopic level; for comparison, a parallel examination was carried out In the hippocampus. We also recorded from amygdala brain slices to examine the voltage-dependent properties of AMPA receptor-mediated evoked synaptic currents in BLA principal neurons. At the light microscopic level, GluR2 immunoreactivity was localized to the perikarya and proximal dendrites of BLA neurons; dense labeling was also present over the pyramidal cell layer of hippocampal subfields CA1 and CA3. In electron micrographs from the BLA, most of the synapses were asymmetrical with pronounced postsynaptic densities (PSD). They contained clear, spherical vesicles apposed to the PSD and were predominantly onto spines (86%), indicating that they are mainly with BLA principal neurons. Only 11% of morphological synapses in the BLA were onto postsynaptic elements that showed GluR2 immunoreactivity, in contrast to hippocampal subfields CA1 and CA3 in which 76% and 71% of postsynaptic elements were labeled (p < 0.001). Synaptic staining in the BLA and hippocampus, when it occurred, was exclusively postsynaptic, and particularly heavy over the PSD. In whole-cell voltage clamp recordings, 72% of BLA principal neurons exhibited AMPA receptor-mediated synaptic currents evoked by external capsule stimulation that were inwardly rectifying. Although BLA principal neurons express perikaryal and proximal dendritic GluR2 immunoreactivity, few synapses onto these neurons express GluR2, and a preponderance of principal neurons have inwardly rectifying AMPA-mediated synaptic currents, suggesting that targeting of GluR2 to synapses is restricted. Many BLA synaptic AMPA receptors are likely to be calcium permeable and could play roles in synaptic plasticity, epileptogenesis and excitoxicity.

Original languageEnglish (US)
Pages (from-to)1728-1738
Number of pages11
JournalJournal of Neurochemistry
Volume94
Issue number6
DOIs
StatePublished - Sep 2005
Externally publishedYes

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Propionates
Synapses
Neurons
Rats
Post-Synaptic Density
Calcium
Ionotropic Glutamate Receptors
bucide
Basolateral Nuclear Complex
Electrons
Hippocampus
Clamping devices
Electric potential
Labeling
Capsules
Plasticity
Light
Immune Sera
Brain
Neurotransmitter Receptor

Keywords

  • AMPA receptor
  • Basolateral amygdala
  • Electron microscopy
  • GluR2 subunit
  • Hippocampus
  • Patch clamp recording

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

Evidence for low GluR2 AMPA receptor subunit expression at synapses in the rat basolateral amygdala. / Gryder, Divina S.; Castaneda, Dora C.; Rogawski, Michael A.

In: Journal of Neurochemistry, Vol. 94, No. 6, 09.2005, p. 1728-1738.

Research output: Contribution to journalArticle

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