Differential involvement of the core and shell subregions of the nucleus accumbens in conditioned cue-induced reinstatement of cocaine seeking in rats.
BACKGROUND
The nucleus accumbens (NAC) is theorized to be a critical element of the neural circuitry that mediates relapse to cocaine seeking. Evidence suggests that the NAC is a functionally heterogeneous structure, and the core (NACc) and shell (NACs) regions of the NAC may play a differential role in stimulus-induced motivated behavior. Thus, determination of the involvement of NAC subregions in conditioned cue-induced reinstatement of cocaine seeking is warranted.


OBJECTIVE
The present study compared the effects of GABA agonist-induced inactivation of the NACc versus NACs on conditioned cue-induced reinstatement of cocaine seeking behavior.


METHODS
Rats were trained to lever press for cocaine infusions (0.20 mg/infusion, IV) paired with presentations of a light-tone stimulus complex. Responding was then allowed to extinguish prior to reinstatement testing. Reinstatement of cocaine seeking (i.e. responses on the previously cocaine-paired lever) was measured in the presence of response-contingent presentation of the light-tone stimulus complex following microinfusion of muscimol+baclofen (Mus+Bac, 0.1/1.0 mM, respectively, 0.3 microl/side) or vehicle into the NACc or NACs. The effects of these manipulations on locomotor activity were also examined.


RESULTS
Mus+Bac-induced inactivation of the NACc abolished, whereas inactivation of the NACs failed to alter, conditioned cue-induced reinstatement of operant responding relative to vehicle pretreatment. Time course analyses of the effects of these manipulations on locomotion versus operant responding confirmed that the effects of Mus+Bac on reinstatement were not due to suppression of general activity.


CONCLUSIONS
The functional integrity of the NACc, but not the NACs, is necessary for conditioned cue-induced reinstatement of cocaine seeking behavior.
Fuchs
Rita A
RA
Department of Physiology and Neuroscience, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA. fuchs@musc.edu
Evans
K Allison
KA
Parker
Macon C
MC
See
Ronald E
RE
D000161:Acoustic Stimulation; D000818:Animals; D003042:Cocaine / Q000008:administration & dosage; D019970:Cocaine-Related Disorders / Q000503:physiopathology* / Q000523:psychology*; D003216:Conditioning, Operant / Q000502:physiology*; D003463:Cues; D005108:Extinction, Psychological / Q000187:drug effects; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009714:Nucleus Accumbens / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence; D012646:Self Administration
D003042:Cocaine