Society for Neuroscience Abstracts 27 (abstract #319.12).

Triple dissociation in the effects of glutamatergic and dopaminergic antagonists in the nucleus accumbens core on the acquisition and performance of appetitive approach to a Pavlovian conditioned stimulus
Patricia Di Ciano, Rudolf N. Cardinal, Rosie Cowell, Simon J. Little, Barry J. Everitt
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK.

Stimuli paired with drugs of abuse can acquire the ability to elicit pavlovian approach responses that depend upon the integrity of the nucleus accumbens. The purpose of the present experiment was to investigate the effects of antagonism of NMDA, AMPA/KA and DA receptors in the nucleus accumbens core on the acquisition and performance of an autoshaping task. Insertion of a CS+ lever into the operant chamber for 10sec was followed by delivery of a food pellet, with no response contingency, while presentation of another lever (CS-) was never followed by food. Subjects developed the conditioned response of approaching and contacting the CS+ selectively, even though their actions did not affect food delivery. A triple dissociation was observed in the effects of AP-5, LY293558 and flupenthixol on the acquisition and performance of this task. The AMPA/KA receptor antagonist LY293558 disrupted discriminated approach during performance only, as evidenced by increased approaches to the CS-. The NMDA receptor antagonist AP-5 impaired only the acquisition of autoshaping. By contrast, infusion of dopamine D1/D2 receptor antagonist flupenthixol decreased approaches to the CS+ during both acquisition and performance. These data suggest a selective role of DA in approach to the CS+, while AMPA/KA and NMDA antagonists are differentially involved in the performance and acquisition of this conditioned response, respectively.