Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

1-6-2010

Publisher

Society for Neuroscience

Source Publication

The Journal of Neuroscience

Source ISSN

0270-6474

Original Item ID

doi: 10.1523/JNEUROSCI.1342-09.2010; PubMed Central: PMCID 2823262

Abstract

A key in understanding the neurobiology of addiction and developing effective pharmacotherapies is revealing drug-induced plasticity that results in heightened relapse susceptibility. Previous studies have demonstrated that increased extracellular glutamate, but not dopamine, in the nucleus accumbens core (NAcc) is necessary for cocaine-induced reinstatement. In this report, we examined whether drug-induced adaptations that are necessary to generate cocaine-induced reinstatement also determine relapse vulnerability. To do this, rats were assigned to self-administer cocaine under conditions resulting in low (2 h/d; 0.5 mg/kg/infusion, i.v.) or high (6 h/d; 1.0 mg/kg/infusion, i.v.) levels of drug intake since these manipulations produce groups of rats exhibiting differences in the magnitude of cocaine-induced reinstatement. Approximately 19 d after the last session, cocaine-induced drug seeking and extracellular levels of glutamate and dopamine in the NAcc were measured. Contrary to our hypothesis, high-intake rats exhibited a more robust cocaine-induced increase in extracellular levels of dopamine but not glutamate. Further, increased reinstatement in high-intake rats was no longer observed when the D1 receptor antagonist SCH-23390 was infused into the NAcc. The sensitized dopamine response to cocaine in high-intake rats may involve blunted cystine–glutamate exchange by system xc. Reduced 14C-cystine uptake through system xc was evident in NAcc tissue slices obtained from high-intake rats, and the augmented dopamine response in these rats was no longer observed when subjects received the cysteine prodrug N-acetyl cysteine. These data reveal a role for drug-induced NAcc dopamine in heightened relapse vulnerability observed in rats with a history of high levels of drug intake.

Comments

Published version. Journal of Neuroscience, Vol. 30, No. 1 (January 2010): 210-217. DOI. © Society for Neuroscience 2010. Used with permission.

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