Long‐term potentiation (LTP) at hippocampal CA3–CA1 synapses is thought to be mediated, at least in part, by an increase in the postsynaptic surface expression of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole proprionic acid (AMPA) receptors induced by N‐methyl‐d‐aspartate (NMDA) receptor activation. While this process was originally attributed to the regulated synaptic insertion of GluA1 (GluR‐A) subunit‐containing AMPA receptors, recent evidence suggests that regulated synaptic trafficking of GluA2 subunits might also contribute to one or several phases of potentiation. However, it has so far been difficult to separate these two mechanisms experimentally. Here we used genetically modified mice lacking the GluA1 subunit (Gria1−/− mice) to investigate GluA1‐independent mechanisms of LTP at CA3–CA1 synapses in transverse hippocampal slices. An extracellular, paired theta‐burst stimulation paradigm induced a robust GluA1‐independent form of LTP lacking the early, rapidly decaying component characteristic of LTP in wild‐type mice. This GluA1‐independent form of LTP was attenuated by inhibitors of neuronal nitric oxide synthase and protein kinase C (PKC), two enzymes known to regulate GluA2 surface expression. Furthermore, the induction of GluA1‐independent potentiation required the activation of GluN2B (NR2B) subunit‐containing NMDA receptors. Our findings support and extend the evidence that LTP at hippocampal CA3–CA1 synapses comprises a rapidly decaying, GluA1‐dependent component and a more sustained, GluA1‐independent component, induced and expressed via a separate mechanism involving GluN2B‐containing NMDA receptors, neuronal nitric oxide synthase and PKC.
Induction and expression of GluA1 (GluR-A)-independent LTP in the hippocampus
C. Romberg,J. Raffel,L. Martin,R. Sprengel,P. Seeburg,J. N. Rawlins,D. Bannerman,O. Paulsen
Published 2009 in European Journal of Neuroscience
ABSTRACT
PUBLICATION RECORD
- Publication year
2009
- Venue
European Journal of Neuroscience
- Publication date
2009-03-01
- Fields of study
Biology, Medicine
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- ca3-ca1 synapses
Hippocampal synaptic connections from CA3 pyramidal neurons to CA1 pyramidal neurons used for the LTP experiments.
Aliases: hippocampal CA3-CA1 synapses
- glua1 (glur-a) subunit
An AMPA receptor subunit that is absent in the knockout mice used here for testing GluA1-dependent mechanisms.
Aliases: GluR-A
- glua1-independent ltp
A form of hippocampal synaptic potentiation that can be expressed without the GluA1 AMPA receptor subunit.
Aliases: GluA1-independent long-term potentiation
- glun2b-containing nmda receptors
NMDA receptors that include the GluN2B subunit and participate in the induction pathway studied here.
Aliases: NR2B-containing NMDA receptors
- gria1−/− mice
Genetically modified mice lacking the Gria1 gene encoding the GluA1 AMPA receptor subunit.
Aliases: GluA1 knockout mice
- neuronal nitric oxide synthase
A nitric-oxide-producing enzyme tested here with pharmacological inhibitors for involvement in synaptic potentiation.
Aliases: nNOS
- paired theta-burst stimulation
An extracellular stimulation protocol that delivers paired theta-pattern bursts to trigger synaptic plasticity.
Aliases: paired TBS
- protein kinase c
A kinase family examined here with inhibitors as a potential regulator of synaptic potentiation.
Aliases: PKC
- wild-type mice
Unmodified mice used as the reference genotype for comparison with the Gria1−/− animals.
Aliases: WT mice
REFERENCES
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