期刊
JOURNAL OF NEUROSCIENCE
卷 27, 期 39, 页码 10621-10635出版社
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.2163-07.2007
关键词
addiction; AMPA receptor; cocaine; nucleus accumbens; rat; sensitization; trafficking
资金
- NIDA NIH HHS [R37 DA015835-05, DA00453, F30 DA019762-03, R01 DA009621, R01 DA015835, R01 DA009621-11, DA09621, K02 DA000453-07, DA015835, R37 DA015835, R01 DA009621-10A1, F30 DA019762-02, K02 DA000453-08, DA019762, K02 DA000453, F30 DA019762, R37 DA015835-04] Funding Source: Medline
Although some studies report increased responsiveness of nucleus accumbens ( NAc) AMPA receptors ( AMPARs) after withdrawal from repeated cocaine treatment, others report decreased responsiveness after withdrawal plus cocaine challenge. Here we examine this apparent contradiction by quantifying cell surface and intracellular AMPAR subunits in the NAc before and after a challenge injection in behaviorally sensitized rats. Because MAPKs ( mitogen- activated protein kinases) regulate AMPAR trafficking and are implicated in addiction, we also evaluated phosphorylation of extracellular signal- regulated kinase ( ERK), c- Jun N- terminal kinase ( JNK), and p38. Glutamate receptor 1 ( GluR1) and GluR2 surface/ intracellular ( S/ I) ratios were increased after 14 d of withdrawal in sensitized rats but were decreased 24 h after challenge with cocaine ( which elicited a sensitized locomotor response) or saline ( which elicited conditioned locomotion). These findings suggested redistribution of GluR1/ 2- containing receptors, a possibility supported by immunoprecipitation experiments indicating that most AMPARs in the NAc are GluR1/ 2 or GluR2/ 3, with few homomeric GluR1 or GluR1/ 3 receptors. In sensitized rats, ERK phosphorylation in the NAc increased during withdrawal and normalized after cocaine challenge. JNK phosphorylation also increased after withdrawal, but after cocaine challenge, it was inversely related to GluR1 and GluR2 S/ I ratios. After saline challenge, p38 phosphorylation was increased. In summary, surface expression of GluR1/ 2- containing AMPARs increased in the NAc of sensitized rats, but AMPARs internalized after a single reexposure to cocaine or cocaine- related cues. ERK phosphorylation paralleled AMPAR surface expression. Although JNK results were complex, JNK and p38 may be involved in AMPAR internalization after cocaine or saline challenge, respectively.
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