Dissociation Of The Core And Shell Subregions Of The Nucleus Accumbens In The Control Of The Fixed Interval Schedule Of Behavior

6. VIRGOLINI, M.B.; BAUTER, M.R.; WESTON, D.D.; CORY-SLECHTA, D.A.

Córdoba, Argentina.

Congreso; XL Reunión Anual SAFE; 2006

Sociedad Argentina de Farmacologia Experimental

In this study we sought to investigate the importance of the nucleus accumbens core (NACc) and NAC shell (NACs), in the regulation of the fixed interval (FI) schedule of reinforcement by microinfusing DA, MK-801, and AMPA in both regions. We also examined the role of the projections from dorsal subiculum (dSub) to NACc, and ventral Sub (vSub) to NACs.  Lidocaine (Lido) administered into Sub and the contralateral projection region was used to inactivate these circuits. Intra-core DA administration increased and intra-shell decreased overall rates. On the other hand, the effects of the injected glutamatergic drugs were undistinguished in core versus shell with MK-801 increasing and AMPA decreasing rates, suggesting that both NMDA and AMPA receptor stimulation blunted rates in both areas by different mechanisms. Furthermore, Lido inactivation of dSub/NACc, but not vSub/NACs, reduced FI rates by decreasing run rates. Lido inactivation coupled with injections of MK-801 or AMPA suggests that MK-801, but not AMPA administration into the contralateral subiculum restored and even increased FI response rates by modifying post-reinforcement pause time. These findings reveal the differential involvement of the NAC subregions in DA- mediated maintenance of FI performance and confirm critical roles for NMDA-mediated subicular projections to NACc.