The contributions of AMPA receptors in the NACs to context-induced relapse of cocaine seeking in rats (2010)

Undergraduates: John Tobben, Xiaohu Xie

Faculty Advisor: Rita Fuchs Lokensgard
Department: Psychology & Neuroscience

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Previous research has implicated the nucleus accumbens shell (NACs) in context-induced reinstatement of cocaine seeking. This study was designed to investigate the role of the ionotropic α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) glutamate receptor in the medial (mNACs) and lateral (ℓNACs) subregions of the NACs in context-induced reinstatement of cocaine-seeking behavior. Rats (N=22) were trained to respond via lever press in a distinct environmental context in order to obtain infusions of cocaine (0.15 mg/infusion, intravenous) on a fixed ratio schedule of reinforcement. Active lever responding was then extinguished in a different environmental context. Using a counterbalanced within subjects design, rats were then exposed to the cocaine-associated or extinction context after bilateral infusions of either vehicle or the AMPA receptor-selective glutamate antagonist CNQX into the mNACs (0.3 µg/µl or 0.03 µg/µl) or ℓNACs (0.3 µg/µl only). During the test sessions, lever pressing was assessed. We found CNQX administered into the mNACs, but not the ℓNACs, dose-dependently attenuated active lever pressing upon re-exposure to the cocaine-paired context relative to vehicle. The same treatment did not alter active lever pressing in the extinction context. These findings suggest that stimulation of AMPA receptor stimulation in the mNACs is necessary for the context-induced reinstatement of cocaine-seeking behavior in rats.